I am looking at using the tube type/dual inner tube transmission cooler.I will be using a 700r4 transmission with a mild converter.This is going in my 1966 Nova.Can anyone tell me if they have had any luck with these and what lenght is recommended?

are you talking about the heat-sink type? I would still run a rad style with an elect. fan.

This is one that is finned about 3" in diameter and in lenghts from 12" longer.