I had a Modine #583 3 row stock replacement radiator. It cooled my 401 fine. I did upgrade to a 4 row radiator, and now I do heat up a little more, but only when I am idleing and moving slow. The problem is that I don't have a fan shroud, as soon as I get some air flow from increased RPM's or moving a little faster, it cools right down. I have also done the CJ Dave bypass modification, but instead of removing the bypass, I restricted it. It didn't seem to make any differance. My recomendation is the Modine 3 row radiator. It was a lot less expensive than my 4 row, and worked just as well.