11 to 1 on pump gas

I have stock 340 compression, around 10.5 with stock J heads, it likes a splash of racing gas to make it happy even with the timing retarded.

Go aluminum heads and you would be OK from what I have been told, and at the cost of aluminum heads why wouldn't you?

I had mine done years before SBM aluminum heads were as available as they are today, should have bought a set the last time it was apart.