Big Block Dart Cooling

Your car should have the 033 radiator. That is a 3 core unit.

I have a new 033 in my 69 cause the correct 065 are extremely hard to get. Run the stock 7 blade fixed fan and shroud with the correct spacer and pulleys. (All Stock)

I had similar issues and put in the FlowCooler pump and high flow 185 Milodon t-stat. Got my timing all sorted and she will hold her temp cruising or idling. I am running an 800 AVS and have blocked the vacuum advance, 20 degrees initial and 35 total all in at 2500RPM. I run 50/50 mix.

That was with 4.56 gears. Just went 3.55 and have not cruised much yet but intend to this weekend.