thoughts on the M11 Cummins?

[Jas2153]

A friend of mine just bought a 97 Freightliner day cab that has an M11 in it that needs to be overhauled. He's looking for some opinions on just how much he would be able to haul with this motor. We're trying to decide if he just should take it out and go with a bigger motor or go with the overhaul. We're in southeast Texas where it's pretty much flat so he won't be going up an hills or mountains. All opinions would be appreciated.