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.
I did have an airdam, that helped pull air through the radiator.
The only problems i had with that carb were big cam + stock head + stock intake related. I felt there was something missing and my restrictive set-up was probably the problem.
I'd say that running with out a thermostat is the/a problem...but you have a restrictor plate to help slow the flow....so...??? I have no idea. I'm sure there are quite a few of us scratching our heads here. Something will come up.
good luck
angelo