Sometimes cars of that time period have engine compartments that contribute to overheating. Their design traps hot air so that no matter how hard the fans are blowing the hot air has no where to escape. When you put a larger V8 in there and toss ac into the mix, it just gets worse.

Does the car cool off when you get it moving again? If so, what does it normally run at? Also, what brand fans are you running?

Don