Trans Cooler

Like these guys said. Use the plate type. I run running two of them instead of a single one for fitment reasons in my '68 Barracuda.

Instead of a thermostat, I use a pair of small ball valves to bypass the coolers in the winter or when I'm just making short trips around town, so the radiator can put some heat in the fluid.
You wouldn't happen to have a couple pictures of your set-up would you?