Shop "trouble"...any advice?

Just sounds like a case of someone trying to do you a favor and got in over his head with no idea how to fix it and probably trying to still make a living working on his other work with your vehicle as a low priority

I have seen it in the past. Glad you got it back and figured out. Sometimes a fresh set of eyes sees things in moments and the original eyes could never see it
I'm super happy to have the car back and now that I've spent quite a few hours on it, it's running amazing.

Still, though, I can't get over the fact that I paid nearly $4K to this shop, plus bought close to $1K in major rebuild parts out of pocket(not to mention the $1250 spent on the head, etc) and there's SOO much stuff that's left undone or just isn't right.

1. They couldn't figure out how to hook up the plug wires correctly
2. The distributor drive gear didn't get installed correctly(fixed that-fortunately not too bad on an engine recently apart)
3. The timing was so far off I'm amazed it ran. It stumped me when I first started messing with it because I couldn't even see the mark under the strobe
4. Carburetor mixture was off my miles, likely related to the fact that they tuned it running on one cylinder and with the timing so far off
5. Carburetor linkages were installed completely wrong such that they couldn't even be adjusted for proper synchronization, etc, plus the throttle didn't reliably close with food off the gas.
6. Related to both the timing and the linkages being set up wrong, I could not get it to idle below ~2K
7. Valves were set with no lash-fortunately I didn't burn one on the way home, but they completely overlooked the lash spec on the cam card.
8. They fitted a 160º TStat because "these car always overheat" despite the fact that I've been running a 195º for years, specifically said that, and the 160º gives me almost no heat plus an engine that does not idle well at low temperatures.
9. It was delivered to me with two different weight oils in the two carburetor dash pots(engine oil in one, ATF in the other)
10. Point gap was too small. That's a minor thing, but I'd have expected them to set it in their tuning.
11. Gearbox oil was low, leading to unreliable overdrive engagement.
12. The spec plug is the Champion N9Y, which crosses to the NGK BP6ES(discontinued, but I have a huge stock of them, and the BPR6ES is a "close enough" replacement). In an effort to get it running better, they'd thrown iridium NGKs with a "5" heat range -that also explains why I still had knocking issues even with the timing set correctly and 93 pump gas.

Those have all been corrected after quite a few hours spent in the garage, and as I said it's running beautifully now.

There are other things left to do, though:

1. There's been an annoying rattle in the gearstick since I got it back. I tore it down last night and there's no anti-rattle bushing. I supplied a fresh one(and spring) plus there was one in the transmission they took out. This is a $3 part, but it's something I'm going to have to order
2. I provided fresh distributor vac advance piping since the one on there is kind of pieced together. That disappeared in all of this.
3. The O/D lockout switch wasn't connected. Since the O/D unit isn't designed to handle the torque of 1st and 2nd gear, there is a switch that prevents the O/D solenoid from engaging unless the transmission is either in 3rd and 4th gear or 4th gear(depending on the year of the transmission). Mine will engage in all gears. A faulty switch would not allow the O/D to work at all, so that means it was bypassed. Since the switch is impossible to change with transmission in the car, I provided a replacement. I also provided a new reverse light switch(identical switch) and there was a good reverse light switch on the old transmission, so they had plenty of them.
4. There's a pesky oil leak seemingly from the transmission that I can't locate.

Also, the car spent the better part of the summer parked outside while they bumped other work in front(not waiting on parts or machine work, just bumping other stuff in front). The dash overlay developed a nasty crack and there's fresh rust on the steering wheel and a few other metal parts. I'm REALLY unhappy about that.

I have it back and I'm glad of that. On one hand, it's been a good project on cold days to get stuff put right, but on the other hand for what I paid for this work I think I have the right to an expectation that the work should have been executed perfectly. A lot of the tuning was rushed, which is not surprising given that they were scrambling to finish it while I was in town. I'm rather resentful over that, and to be honest given all of this I think that the final close to $800 check I wrote them to pick it up really should have been "let's call it even" especially given that they delivered a nearly undriveable car to me that only managed 40mph going downhill.

BTW, it's worth mentioning that I was billed on the final bill for parts I supplied. I asked about those and was given a vague "We didn't see those"(probably really "we lost them"). That included things like timing keys, core plugs(not expensive at least) and a few other odds and ends.

Still, though, since I have fixed a lot of the major mechanical goofs I suppose I "own" them now and can't prove it. For sure I've blacklisted the shop. If I brought the list to them, I might ask for compensation in the form of something like replacing the dash overlay that they let cook in the sun, but that's neither her nor there.
Earlier on in this saga, I was giving the shop the benefit of the doubt, having been in the niche car hobby for ~40 years, but seeing the above I would have a serious Come to Jesus meeting with your contact there. I believe you are owed some consideration given what was left undone, or just wrongly done on the car.

I hope you didn't pay the final bill yet (assuming there was another bill after the $800) and prior to paying I would talk to them and start the meeting by articulating the points above and reflect their value in what YOU would pay as a closeout.

Again, good luck!
Hard to believe they specialise in this stuff...or the boss gave the job to someone who ''says'' they know all about them. It's still too easy to get something wrong even if you know certain vehicles inside and out, I have plenty of Duh moments myself, but that's an awful lot of things not sorted.

I used to use 160 thermostats in my B Blocks - they are just one hill away from burning a valve, blowing a headgasket or cracking a head. 1200 B Block in my A40 had 17 cracks, all repaired. No heaters. Also used to have overdrive in all gears...split shift like a twin stick or Eaton 2 speed diff. NZ in the '70's, a different world and doesn't apply to you in 2021.
I'm about 1K miles into driving it, and I'm at a point where I'm feeling really, really good about how everything is running. The engine runs smooth and pulls strong all the way up to 5K, and right now I'm at a point of just mostly being able to enjoy the car.

It took me a fair bit of work to set the car "right" after getting it back. I gave the list above, and I've finally sorted it all. Lately, especially when it was stupid cold(but I could tolerate working in the garage) I've spent time working on a backlog of other projects and parts that have been on the shelf for years. I've been fighting with getting a working radio, and I have a great Motorola now that unfortunately is going to take some finessing to get to fit!. I did fit headlight relays from a guy up in Canada who makes more or less drop in kits, and that made a night and day difference in headlight brightness. I still have hood and trunk struts to install. I've put door cards in that I've had kicking around for a while, and that transforms the look of the car. I have fresh brakes all around after putting that off for years.

Today was a beautiful day, so it was time to drive! 100 uneventful miles on the clock.

Thanks for the update and the pic of your car, it's wonderful, I love those things, they have character, something most cars today
lack entirely.
Nice to see real bumpers on a NA MGB - those side reflectors are hideous though.

When I went shopping, chrome bumper was at the top of my list. BTW, when the 5mph rubbers were required in the US, all cars regardless of destination got them, presumably because they needed major body changes(they were a bit ahead of their time in integrating the bumper into the front end so well, but that also means that chrome bumpers aren't a straight forward bolt on for rubber bumper cars) and NA was roughly 90% of the market for MGBs per the sales figures I've seen(500K total made, 400K to NA).

That's not just chrome, though. One of the things I did last weekend was swap out a nasty reproduction that was on the car when I bought it for a not as pretty but actually correctly fitting original chrome. BTW, the original weighs probably 1.5x what a repro does because the repro is such thin steel.
I read most of the posts and I have came to the conclusion that whomever worked on the car really didn't know what they were doing at all. Those cars are basically fairly simple for a skilled auto mechanic. I have a couple shops around my area that could have sorted out your problems without any trouble at all. I sure wouldn't want them working on a very complicated engine that's for sure. A friend of mine used to have a car just like yours with the same color paint and everything. He is deceased now but owned it for a long time and he really like that car. Good to hear you have things sorted out.