This is what they call a late 850 dozer (non letter). The original 850 model (roughly 1975). I’d like to keep the original radiator and just plug the transmission oil cooler ports on the bottom. This should keep the engine radiator running normal. I saw the later models used the side by side radiator/oil coolers but they are crazy expensive as a package. I just don’t know how to size an external oil cooler.