How much weight do you tow? and with how much motor?

I would find a Cummins ISC 300 HP which will have 1000 ft lbs of torque while it's the ISB 300 HP that only has 660. Many adds do not tell you which 300 HP Cummins the MH has. Compared to the 8.3L ISC the 7.2L Cat (3126/C7) is only OK. Yes I had a 40' DP with a 330 HP 3126.
My gross combined weight is 45K and the ISL 400 (a stroked ISC) does surprising well.