My mom was in the concession business for 30 years and she pulled her trailer to shows all over Oklahoma with a motorhome that had a 454 and turbo 400 in it. Went through 3 transmissions before we had him put one in, lasted 10 years I think. It was way overloaded but held up good I thought. We had a pretty big name drag racing transmission guy in Moore build one and I think it lasted one season, then he wouldn't stand by it. Ol Baker at American knows his stuff, think some of the guys that work there have been with him for 30 years.He did one for me about 15 years ago. It outlived the truck. I'd guess it made it about 150K miles before the engine broke and the truck was sold for parts.
And yes, it seems like I'm forever getting transmissions rebuilt, but rarely on the same