Underdrive pulleys and overheating?

Put your old stuff that worked back on. Problem solved.
I read all of the cooling threads and 9 times out of 10, the cooling problem is an owner trying to reinvent the wheel.

My engine is much like yours. A bit more radical actually.

I could start it and let it idle on a 100 degree day until it ran out of gas and it wouldn't overheat.

My cooling system is 100% stock 68, 340 stuff except for the $30 NAPA stock replacement water pump.