318 Poly Vibration

How long did you let it run after you started it again (after a half hour)? Is it possible it heat soaked and just needed to clear itself out? Modern gas seems to expand easily with heat, and many old cars will run a little ragged for a few minutes after a hot start. Your plugs look like they're a little wet, like they might have some gas on them, and they shouldn't be that black.

It seems rich...have you checked the fuel pressure? Blown out the carburetor air bleeds with some cleaner/compressed air?

Sorry if you've already covered this...I just read your last few posts.