I am getting ready to put a slightly modified 351w into my 69 GT350. Its 30 over and has a CR of about 11.5-12:1 ish .The car has A/C & I live in PalmSprings heat . The builder of my engine said, It might be better for me to get another radiator that had a "better" cooling capability than the original radiator that is in it. I think the original is a 24x15x2? . Can anyone with experience,etc give me an idea the size radiator I might want to get?