I know you asked fan or rad and I'm sure this isnt what you want to hear but to me its both. Check the inlet and outlet of the rad with a IR thermometer. Good delta? If not, try a box fan in front, make any difference? Dont mean to be all over the map but I'm tired.
Timing good? Not too lean? I had exhaust issues at first, that heated up the engine bay quite a bit too.
Summit sells a rad too
Radiator Style: Crossflow
Overall Width (in): 30.750 in.
Overall Height (in): 15.875 in.
Overall Thickness (in): 3.125 in.