FWIW...I had a 12.2:1 compression 440 w/ 915 iron heads that cranked 220 psi w the 509/292 MP hyd cam. It ran GREAT on 100LL AvGas.

My uncle's '68 GTX had a low compression flattop piston 440 w/ open chamber heads and a mild cam. It didn't have much compression, cranked around 170 psi if I recall correctly, but the quench was non existent. It pinged terribly w/ 93 octane and anything more than 30° timing. Splashed in some 100LL, cranked the timing back to 38°, and it was a different animal.