350K miles on the NV4500 in my 97 2500 5.9 4x4. Truck spent most of it's life hauling boats up for a dealer so nothing as heavy as what rhinodart is probably doing with his trucks.

If you're wanting to do a conversion, I think you're going to have to snag everything from another Cummins truck. IIRC the input shaft spline count is different on your a/t transfer case than on a m/t transfer case.