How large of a transmisson cooler do you guys run? I had a 12000 GVW (5" x 12-1/2" x 3/4" with 4 passes) on my car and the trans would be 190 degrees at 3rd round and get to around 230ish if I made it to the finals. I upgraded to a 18000 GVW (7-1/2" x 12-1/2" x 3/4 6 passes) but didn't really seem to help with cooling much better, still reached 210 for the final round. My car seems to work best when the trans temp is 180-190ish, so I'm thinking about going to an even larger cooler, but not sure how much larger to go.

Something to consider is the type of cooler. There is the Tube&Fin, which is the most popular because it is the least expensive. The other is what is called a Stack Plate style. In the tube&fin, the oil is routed through a steel tube in a serpentine fashion with the heat transfering to the fins. The stacked plate design routes the oil through small channels and transfering the heat to a series of plates. The big difference is how much surface area the oil comes in contact with and how fast the oil flows through the cooler. You can flow oil through a cooler too fast and not reduce its temperature much. On both accounts the stacked plate cooler is superior but 2 or 3 times the money.

largest stack plate one you can fit (not sure what sizes are available but might need to plumb 2 in series). I will defer to Kunkel on this but if the internal cooling fluid passages in/out behind the 2 brass fittings are larger than the brass fitting ID itself then could go to larger fittings and 3/8" lines for more flow (along w a 3/8" cooler of course). Even on a streeter I use the largest surface area I can & I am not convinced a trans can run too cool EDIT but w you being a dragger being too cool is not even an issue

Ferd Exploder's have the stacked plate coolers, many others also I'm sure. Raid the Junk Yard, and put them in a series.

B&M super cooler

I run 2 coolers. Second one helped tremendously

Sounds like you may need a fan on the cooler to get more airflow, and then allow the fluid to circulate through the cooler?