I think your heads are just fine, might be just a hair much on the cam, I'd definantley go with a dual plane intake.
I think the carbs a bit much 750 would be my choice, I don't think 40 degrees timing on pump gas is realistic ( we ran 38 total on mine and that was a alky motor), of course take this all with a grain of salt as I am by no means an expert engine builder, just an old fart with a lot of experiance (LOL)