I have been following this thread with interest. This probably isn’t what you are wanting to here but here goes. I had the same problem with my 69 Bee only difference is I have air and had a three core aluminum radiator in it. The radiator was from a n online bargain dealer. I can’t even find him on line now. Since the radiator was new I figured it wasn’t the problem so I started changing things, pump, fans, thermostats, timing, carb tuning, chasing the problem. Nothing helped. Then one day I put a bigger diameter fan on it to see if that would help. Well it helped aright when the fan flexed forward at high rpm and took out the radiator. I ordered a four core radiator from Champion and got a Chrysler 300C electric fan off Ebag for $90. The difference in the core structure between the no name radiator and the Champion was mind boggling. I installed the new parts and the cooling problem is fixed. I drove the car this week in 90 degree temps with the AC on in traffic in town an out on the open high way. It never went above 180 degrees. This is with a 512 wedge.