My first two cars were a 1973 Pontiac Catalina with a 400 Pontiac and 1973 Bonneville Wagon with a Pontiac 455. Both of them had a TH375. My grandfather towed a travel trailer all over the desert southwest for over 210,000 miles with the Catalina on the original transmission. The Catalina was my first car. I killed that transmission with just over 300,000 miles on the clock and I wasn't easy on that beast. The motor lived on in the Bonnie Wagon after I discovered why you don't rev a 455 into the stratosphere.
My 1976 Delta 88, 1976 Grand Prix, and 1975 Cutlass had TH375 transmissions too. Never had a Chevy with one but supposedly they did exist.
There were at least two TH375 transmissions.
The early TH375 is a Medium duty TH400. It has TH375 cast into the transmission body. This one is a TH400 with one less clutch in each drum and an output shaft with TH350 diameter and splines. It's a pretty stout transmission.
The TH375B is a Heavy duty TH350. This one is still pretty stout but not as stout as the earlier TH375.
If it works and it's the right bellhousing pattern I wouldn't hesitate to use it... Or you could put a 350 Rocket in your truck.