360 Running Issue(s)?

This just "sounds" more like fuel

I would get "rid of" the entire wiring harness, electrically speaking. Got downtown, NAPA, Rad shack, etc and get some alligator clips, and make up a couple of good heavy, no14 or so clip leads. Determine which side of the ballast is the "switch" side, and hot wire the ignition by clipping from that side of the ballast directly to a battery point, starter relay, etc.

IF the problem goes away, you know its in the harness.

Also remove all the connectors, distributor, ballast, ECU, inspect for corrosion, and "work" them in/ out to "scrub" them clean, and "feel" for tightness of the connectors