As to the Ford 300 crankshaft being weak, we ran a 300 with modified 4 barrel carb, 4 speed, and headers in a Ford van for over 500K miles. The head was never off the engine. Engine was still strong when body rusted out for the third time (I love salt and cinders!!!).

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor you will ever buy, is the incorrect one you attempt to modify!!!