'97 & up "Center Lube" 4L80E's have the smooth Band & Reaction Carrier, Though you can use early "grooved" Band on a late Reaction Carrier......Don't use a Late Band on a Early Carrier.
I like to use OE TH400 Grooved Bands on ALL my TH400/4L80E builds.....But they are getting tough to find.
Accumulator valve spring and shift feed hole questions.They get damaged from the manual shift shaft getting banged around. If the nail doesn't just fall out.....See if you can get it turning (Lineman Pliers work best), Pull straight on the nail while turning it counter clockwise.
They can be quite bent & not turn, I use a small dent puller/slide hammer with a 10-1.50mm nut on the end of manual shift shaft to straighten the nail out. You may have to use the lineman pliers to keep the nail in the same orientation.
There are tools to change the shift shaft seal without removing the shift shaft!