Not leaving this hanging, just haven't touched the truck again until today!
Went out this morning and did the following:
Sprayed starting fluid in past the throttle body and then tried to start it. Got some pops (maybe 1 per 3-4 seconds) and some vapor out the tailpipe while cranking but no start. So, different behavior but different enough to point to fuel as the problem? Doesn't seem like it to me but I don't know.
Then I checked compression on cylinders 1 and 2 (front cylinder from each bank). The book I have inexplicably doesn't seem to contain the compression test specs but I got a solid 150 PSI on both cylinders which seems fine to me (9:1 compression ratio) and probably rules out valve timing.
The plugs I took out looked fine I think (a little wet from the cranking) but the gap is a little wide (0.065 vs spec of 0.060). Not sure if that could contribute but I'm sure it doesn't help. Not looking forward to it but I should probably just replace them all.
Then, I hooked up my timing light to a variety of cylinders and noted that while they were all firing, some of them seemed less frequent than others and one was firing at probably twice the rate of the others. Seems to me this is the clearest piece of evidence yet and it points to either the cap or the rotor.
My current thinking is, then, that I should take off the upper intake and pull/inspect the cap and rotor. I feel like I should probably replace both of those, and the plugs and possibly the wires while I'm in there (although the wire sets can get kind of pricey so maybe I should test them instead). Not sure about the coil.