Transmission Cooling

I am building 38 Ford street rod, crate 350, th350 trans. I need help on trans cooling for gulf coast Texas. I want to rail mount under car. What should I use and how much cooling is required. How do I size....fin/tube , heat sink design. (heat sink manuf recom'd 28" X 3" dia.) I have 2 areas ~5x14 " for mounting. I would appreciate any suggestions. thanks

if you are going to mount it under the car where it will not get a lot of air....get the biggest cooler that you can. Maybe even put 2 in series, one on each side.