Why on earth do you want 500hp with those tires?
That's asking for a guardrail view at 70...lol. I used to spin those tires with 3.23s with a sprayed 340 making about 450hp in 3rd gear. The tires are not tall. Closer to 25", so at 70, with 3.23s, you're looking at about 3100rpm cruise. IMO, the best choice for you use wont make 500 hp with that package, but will be dead reliable for a very long time with no maintenance and make close to 500. More important, they will make serious torque. Basically something in the 235-240°@.050 range is what I'd go with. You aren't building anything huge. In fact, with those heads and valve shrouding, a larger cam simply wont make much more power. Because of that I would notch the bores too. I'd set static compression at 10.5:1 with a .030 quench and run the Comp XE284H hydraulic. You could go faster rate of lift, you could go with more lift. I dont think it will help much and will cause more risk of flattening due to idle time and heavy springs. That's how I'd build. I'd really recommend a 15" wheel and wider tires too...
