My combo was head limited at 557 cubes. I have a 4.5" stroke with 4.440 bore. Last time I was running at the track it was consistent 9.0 car and dipped into the 8's a couple of times on a good track. It made right around 850 HP and race weight was 3000#. I have hand ported -1 heads. It was ~15:1 with a .750/.720 cam. Peak HP 850@7200 and peak TQ 722@5500. Build as big as you can, you can always swap pistons/heads later. I'm in the process of taming it for pump gas and street use, I can't wait to see how it does at 11:1 and 93 octane gas

Picture is my head flow data from 2 different benches. MCH exhaust numbers are with a short header tube, PRH ex numbers don't have a tube attached.