transmission cooler

You should be able to find an adapter to go from screw type fittings to barb.
Have you cleaned the debris out between AC condensor and the radiator? You can normally loosen the AC condensor and then blow out the debris with a comprassor.

https://www.carid.com/images/bm/cooling-systems/pdf/coolers-user-guide.pdf

I have a B&M cooler that has fitting but will it connect to your fitting. Only you can decide.

Any good hydraulic hose shop can help you. Ideally, for flexible plumbing, IMO, you should use swaged fittings on the cooler if you want a reliable connection. If it's hard connected, then flare nuts are the way to go.

When you say the ATF is hot, . . . . how hot? It's normal for the ATF to heat up (quite a bit) under load. The engineers that initially sized the ATF cooler designed the system to keep the ATF within acceptable limits at maximum towing capacity and extreme temperatures. Generally, they don't guess, especially on truck chassis. Are you having a specific problem, or are you thinking that you might? The numbers tell the truth.

Chum lee

Also, you need to be able to not "OVER-COOL" in cooler temperatures.

Though the mechanics is a bit different, I installed a fuel cooler on the return line on my DP. Like ATF, there IS such as thing as fluid being too cool.

So, made a cover for the cooler that velcro's in place for winter driving.

Google Derale 13960. I installed one of these in my Class A, it works perfectly. The thermostat is set at 180, so over cooling isn't an issue. I placed it in series with the factory radiator cooler just before the return to the transmission (after the radiator). Installation is easy, you need to run a 12 volt feed, the thermostat grounds the circuit.