Engine kills when hot: Round 2

[BarnabyHooge]

After replacing the intake gasket my old problem is still a problem. It's a '71 350.

The motor runs fine when it's cool. Idles pretty steady at 1000 in Park and 800 in Drive & Reverse. It's noticeably smoother now than it was before the new gasket. I can move it between the 3 with no problem.

After a while of city driving or just when the engine gets really warm (about 190 water temp), then motor will kill when it's at a stop. It doesn't bounce around first or make any sort of warning sign that it's about to go, the tac just drops.

Restarts with no problem, fires up as normal.

The only way it stays running is if I keep a slight touch on the accelerator at a stop with my other foot on the brake.

I've redone the plugs and fuel filters have all been replaced.

Any ideas? Any other tests that might help me figure this one out? I'm at wits end with this after my troublesome intake replacement.