I noticed you mentioned heat buildup while towing, what kind of mods do you have inside your transmission? What are you trans temps looking like while pulling the trailer uphill, flat highway, etc)???
My goal was to be able to hold the pedal to the metal and not have temp problems. To that end I pulled out the 93 radiator and intercooler and installed a set from a 2000 truck. I also dumped the stock oil to water cooler for the transmission because I was tired of engine temp and transmission temp fighting each other and being interdependent. I installed two of the largest Derale fan assist plate and fin coolers I could find in the frame between the Tcase and fuel tanks.
transmission was replaced at 250K with a standard ATS transmission and TC. Overall I am happy with the transmission, I feel llike the TC could be tighter (maybe just a lower stall by 200 rpm) though after hearing people talk about the DTT one, still MUCH better than the stock one. transmission fluid has always been changed yearly at 10-15K miles, never appeared burnt even in stock unit after 250K.
Running down the road in under 70 temps empty (in overdrive) the transmission sits at 130, climbing my 6% pass to work I get to about 190. With the trailer in tow I run about 190 on the flat at 60 in od, and hills the temp climbs pretty good in od. I go into 3rd gear with the trailer and to be honest I can run 150 in the flat and about 190 on a 6-7% grade at 55. In 3rd gear I can't get the transmission over 210.
A couple things I have noticed:
transmission temp drops if I can hold 70 up hills in od vs 60 (stall speed on TC must be between those speeds). I think lower gearing or a tigter converter would help this.
Right now I can keep transmission temps under 230 in OD as long as I stay under 15-18 lb boost. This is for hills or headwinds, whatever loads the truck.
With the 2000 intercooler and full 4" exhaust and "normal" pump tweaks I do not see over 1300 egt as an absolute max (5-8 min under full load climbing, not a "spike like the 1/4 mile").
Max boost is 27-28 psi, keep boost under 22-23 psi and EGT stays at 1000 degrees. This seems to match common wisdom that the H1C falls off around 23 psi and is less efficient.
This kind of started to ramble didn't it, well I hope you can find what you want in it.