I think the truck might have just been [censored] off I left it behind the house full of corn for so long.
Put the charged battery in, jacked around with it for another 5 minutes or so, and now it fires right up every time again.
Might have been a combination of that valve not getting open/closed right and that gunky carb, compounded by not having started it in a week or so. . i dunno, but it's runnin' like a top again.
But I can still appreciate why some folks opt to switch to modern motors.. man I was close to just putting it on a trailer and taking it to the mechanc and saying, "Don't call me till she's runnin low 9's at the track!"