I put 40K on a "diesel built" TH700R4 behind my 6.2L Banks turbo. No problems. I know that the 4L80-E is more robust, being an evolutionary advancement beyond the TH400 3-speed non-OD.

A fellow east coast member came to a couple of our first Rendezvous here in Montana. He drove a late 1980's 1500 Suburban powered by a Banks turbocharged 6.2L diesel. That Suburban had a TH700R4, and he towed a 36' triple axle Airstream all over the country.

We've produced two different articles on building a reliable 700 for the 6.2/6.5. Gotta use the right parts... use the right TC and do it all with the right case.