I am also mocking up the transmission cooler. Specced a Derale 17 row plate/fin cooler. Will have to plumb it in as a stand alone with a trans cooler thermostat since the 42RH uses 3/8" lines. Going to hit the wrecking yard for a set of 3/8" trans lines off a 1990-1992 V8 ram van . I scoped out the wrecking yard today and found 2 candidates I can pull em from. I used the dimensions at the Derale website to make a cardboard mockup to figure how I want to mount the cooler, and to be sure I have enough room to fit it since i havent ordered it yet. Also plan on using a 69 camaro Z/28 chin spoiler as others here have done. This will help air flow through the cooler and radiator.