Just use the stock radiator and have a 4 row core installed, it will never over heat, my 383 has 496 hp, 26" rad, with a 4 row core, and it could sit in traffic all day at 195. in the hot summer!! My friend also, with a built 470" 568 hp, has a 22" rad. and a 4 row also, runs at 200 degrees, but no higher, we both have a 7 blade fan with a fan clutch, and shroud, hope this helps.