I have two b-body cars and both have 440's with 22" radiators. one is stock, all iron engine, stock exhaust, ramcharger fresh air stuff, etc. this one won't run cool in the summer with a 3 row brass radiator; about 325hp. the second one has alum top end, headers, cam, etc and won't run hot if you drove it thru hell. the second has a 4 row brass radiator; about 450hp. I don't think horsepower ratings on radiators means much. how much time are you going to spend at 600hp vs 50hp? a lot of factors other than horsepower.