[sick472]

I have a 85 K20 with a 350 and it does something very similar. I have found that a few of my plugs are fouling with what appears to be oil (the old engine uses oil pretty bad). If I pull the fouled plugs and clean them or replace them, it buys some more time. I think my valve seals are leaking in those cylinders (good compression tests), not so much that I witness oil smoke from the exhaust,but enough to foul the plugs over the course of a few months.

Hopefully your stalling is fuel filter, vapor lock, or gas cap related.