I worked with Ron Davis and Joe (cooler towing) to make my dual pass radiator. It was not cheap but it wasn’t 2400 bucks. This was back in 2018 though as well. Joe and Ron understood how full retard I was about towing with the limo and actually wanted to help while giving suggestions as well.
The aux radiator I had/brad has came from Joe at cooler towing as well.
Considering the coin I had in the engine, transmission, diffs, and everything else in the limo, a few grand for a good drop in coolant temps was worth it. Ron’s rads are also extremely well known in the off road world for robustness and won’t fail like a mishimoto or other aftermarket ones for dmax’es. My first dual pass started to leak. No questions asked, Ron built an entire new one with additional bracing and 0 leaks since. He since updated all the others with that bracing.