Lowlife,
Water cools 32 times more efficently than air. Aftermarket coolers are made as additional cooling only. To run the trans with water cooling you will need a radiator with a cooler.
I always treat 2nd hand autos as cores. You may get lucky and be able to run one for a while.
Early autos have thier share of issues, are expensive to repair and hard to get parts for. It may be cheaper and better to go with something else. Of course depending on your budget.
Cheers
Warren
Grizzly (Aussie Mainline)