Cold and hot are subjectively ambiguous .
You are looking for a temperature difference from top to bottom tanks NOT rubber hoses. Some say you need 50 degrees.
I run 30* which works fine. But I admit, my alloy heads radiate a lot of heat, even with multiple coats of hugger-Orange on them, lol.
If you are running hot at speed, an aluminum rad may not solve your perceived problem. My rad is from a 1973 Dart Swinger 318 with A/C . it's doing a fine job in the original slanty core support.