As Don said, this topic has been hashed before.....we have an external fin cooler on a Jeep with a 700R4. We made it using extrusion that you can buy and cut to length:
http://www.alumrad.com/coolers.htm
The cooler replaced a B&M Super Cooler and apparently did an equivalent job. Make sure to mount the cooler away from heat sources (like exhaust pipes) and somewhere where there is air flow. Obviously, at rest, the no cooler has air passing over it unless there is a fan involved....that's why a radiator mounted cooler is preferred. In your case, stacking an evaporator, a radiator and a trans cooler in series would be hokey.....

Try the linear cooler, they're really cheap.

mike in tucson