just curious you say the 140 is 400 lbs heavier than the 120? how much do these things weigh?

I changed the transmission cooler in my Chevy Silverado to a larger, after market unit because I was towing a heavt trailer a long way at highway speed. I mounted it in front of the radiator where the old one was located. I built a mount for it out of aluminum angle although the unit I bought came with cable ties that they expected to be pushed through the radiator for mounting the cooler. It was pretty easy to do. All the lines were rubber. No bleeding involved.

I'd take a hard look at converting to standard trans.