I figure the V6 3L will be fine if not towing heavy stuff or large stuff like and enclosed trailer. I would not want to have something that small for heavy high speed towing though; I expect it will not last nearly as well. I bet the 1500 trannie wil be lighter too.
For the OP, if he is looking at used Ram 2500 or 3500 CTD, I would go for the '07-04 5.9L. The 6.7L came out in late '07 and the mileage dropped due to the lower compression for NoX. (Thanks a lot, EPA!!)
Dodge frame are the ligthest of the big 3 so be ready to rebuidl stuff more frequently. But I have had C20 6.2L NA diesel and have a 7.3L Ford F350, but like the Dodge with the CTD best of all. Just a better driving truck both for power and handling, even with the 4WD. All 3 towed will and were/are crew cabs; the longer wheel base sure amkes towing stable.
And for the guy with the Chevy that takes a 40 acre plot for turning....my '84 Chevy was the same way....must be a Chevy 'feature' !