An aluminum block, 540 cubes, ported 440-1 heads or similar will get you 800 hp with an easy on parts cam with maybe . 750 lift, 280/290/110 duration. I would go bushed lifters and rockers. Needle bearings are trouble. I liked the Isky RR 735 cam, .760 lift with 1.55 rockers. With methanol injection, at about 13.5 compression I dynoed 847 hp and went 8.77 at 153 mph at 3000 lbs. That was a megablock 528. I would guess a 528 or 540 using a 4.500 bore will be easier on bearings and crank. Bigger would be nice, but might not have the life between rebuilds that a well used race car needs.