I've run the Holley/Weber(holley5200/weber DFEV pinto carb) for a long time. I had a B210 radiator and a 185deg thermostat. I didnt have over heating problems. It would get hot if i drove fast ( at about 4500 rpms and up in 5th) on a hot day (90+deg) for a long time.
What I mean by 'it would get hot' is the water temp would go up to about 215deg and the oil temp would get to 200. I figured if I was driving 85-95mph for 3-4hrs straight (SF to LA via Hwy 5) that those temps are 'normal' .
I have SU's now and i does the samething. Now i watch the EGT gauge and make sure it doesnt get over 1300deg or the coating on the headers will get messed up. (i just thought of a new topic)
Have you tried to richen up the carb? Just to see what happens. Find some old jets from a Ford/holley/weber and drill them out.