I can vouch for the Northern Radiator as well as their Trans cooler. Installed both after my radiator split the plastic on my way to the Hill in AZ. I typically average only 80 Deg over ambient vs the 100 or so before. This is both towing or empty in stop and go traffic in AZ heat. In the hills temp will creep up but comes down quicker when the fan kicks in.
www.northernradiator.com
Northern Radiator | GM Transmission Oil Cooler Kit - 12 1/2 x 7 3/4 x 2
Z18060 GM Transmission Oil Cooler Kit - 12 1/2 x 7 3/4 x 2