68 Valiant dies and runs lumpy, then suddenly runs fine.
I've replaced all the factory fuel routing, and the fuel filter is mostly new... Carb rebuilt just a few hundred miles ago.
The issue hasn't popped up since. My best guess is something along the lines of spark just judging by the lack of change when I pulled spark plug wires. I'll be upgrading to an HEI system as soon as I get another paycheck (on a one month break between terms).
I'll give more clues if this pops up again, but for the meantime she's happy. Thanks for all the help everyone!