I would say it's probably 60/40 trail driving to towing. Considering I only put about 3,000 miles a year on the truck, it's not a ton of miles doing either one.
As much as we'd like to do more, we probably only get in 3 camping trips a year which involves towing a 4000lbs camper. I figure with the truck, family, gear, and camper, we've got a GVW of nearly 14K. As
@Kay86K5 mentioned, camping generally involves driving over mountain passes. The stock 454 does great pulling just the truck up and over the passes, it's really adding the camper and etc that makes it hard. It can do it, it's just slow and pushes the motor to the limits. My thought process is that if it had more power, these pulls wouldn't be so hard on it. Plus we really want to get the AC added so that would be another load on the motor.
The other factor is just the fun of having a "high" HP motor which I've never owned before.
I mentioned earlier in the thread (I think) the biggest thing I dislike about the crew cab is showing up to trail runs with a big 4 door pickup with only me in cab. I sometimes think I would like to get a side by side that I would haul to the trails with my crew cab. That would be for the fun weekend get away stuff, but I would still have the crew cab for doing trails with other CK5ers.
To sum it up, the crew cab is our mountain get away vehicle.
A cummins swap worries me because I have no idea about working on diesel trucks. My buddy is doing a cummins swap in his GMT400 and it's not striking me as a simple swap. He also had to go to some pretty big measures to find a good donor motor. He remarked that people around here want a lot of money for their cummins trucks. I think if I really decided I needed to go diesel, I would look at an early Dmax and do an SAS swap and it would replace the crew cab.