Hi Bill,
I think 1,450 ft pounds is the max torque avaliable on Cummins M11s. Cummins can reset your ECM to owner operator specs for about 1/2 hour labor charge. this includes removing the governor, and increasing max RPM to 2,100. You can get a printout of the engine history of the at the same time.
I don't know a thing about the transmission you guys are discussing, but before installing any different tranny, make certain the tranny's torque rating meets or exceeds engine torque output.
onezman
http://onezman.tripod.com/yourrvhaulercom