http://www.grandprixforums.net/threads/91937-9C1-Transmission-Cooler-on-Grand-Prix

^^This is what I did for the trans cooler on my GTP. It was an actual 9C1 transmission cooler with oem lines and everything. Temp drop was about 15*, so nothing particularly awesome, but just a little extra.

I put a larger stacked plate cooler on the 04 Imp LS, and installed it standalone. Dropped temps considerably more.