Transmission Temp... What range do I want to be in? -High Stall Converter

I have the same setup, 9.5" 4,400 flash, same engine. I have the deep B&M 4q extra capacity pan and a 18" x 10" aluminum cooler in front of the radiator. I don't run the lines through the radiator. Anyway after a long Saturday cruise the cooler is barely even warm. I don't run a gauge and I run one quart less.