906 vs 452 heads on 440

Air in, power exploited as completely as possible, and air out.
If the work was done well to a modern, high quality level, and the camshaft is big enough with properly matched components, you should be at 1hp/inch. If you're not, something is off. You need about 220cfm at .500 a cam that opens the valve far enough for long enough, and enough efficiency that it's all put to good use and you're there. The more power you want, the more critical each piece of the puzzle is.
I do not feel that high static is a help if you're running open chambered heads. Something in the 9.5-9.8:1 is plenty. That's because a smaller cam will work better with available fuels and average tuning. I've run as high as 10.8 with iron open chambers but you better be spot on with the tune-up and any load of cheap pump fuel could throw a wrench in that tune. I wouldn't recommend it because static ratio simply is not needed. So given your 10.3 static, I'd be looking at cams with at least 250* @ .050 and you will still want to make sure you get quality pump fuel at 91-93 octane and tune it very carefully. A cam of that size, with lightly modified (read as stage 2 ported) iron heads that can move 250-260cfm at the cam's max lift, with the matched intake and exhaust components, with good ring seal, will make 500hp.