It doesn't only make a difference how many rows of tubes there are in the rad but also the over-all thickness of the core. A 2 inch 3-row is likely to cool better than a 1.5 inch 4-row. Also the shroud position makes a significant difference. It should ideally be within 3/4 in from the fanblade tips all the way around and extend 2/3 into the fan swath. Shrouds that don't reach the fan swath are almost useless.
Another trick is to help the hot air escape the engine bay by cutting holes or louvers into the inner fenders or installing a non-functioning coil-induction style hoodscoop to help clear out this hot air a.s.a.p. A friend of mine worked att a rad-shop, had the best rad etc in his hi-po 289 '64 Fairlane but it kept running hot untill he re-adjusted the hood hinges so the back of the hood was raised abit to clear out the hot engine bay air and it cured the problem. Hope these pointers help sumbody out.
