here is a pump gas 502 made into a 509, that I built for a local guy. It was a gm perf. 502/502 core engine, and thats exactly what it turned out to be. So, we threw away every part, except the block, crank, and head cores, which are 2.25 intake valve edelbrock Perf. Rpm oval port heads that say GM performance parts. Not bad, $7500, 1 year, and throw everything away. But anyhow, with a fairly radical port job on those heads, and a 270-278 at .050 solid roller on pump gas, with a Victor 4500, and a 1050 carb, it made 735hp and 650 ft/lbs.
If you ran more compression, and the heads you have have more potential, it could make a lot of power. Where are you located, I am in St.paul,Mn, I noticed you said you run in Mn. If want any further details, let me know
Frank
Advanced Performance
www.get-ap.com