it depends what type of offroading your planning. I love my 6.2 and it probably runs poorer than most. I mostly crawl up ravines, hills, dry creek beds, etc. (no rocks here) It's great for this low speed, low rpm stuff I just put it in 4LO & go & it runs the same at any angle no matter how extreme. I've had it on it's nose so bad I had to push hard against the wheel to stay off it.
I would say the biggest drawback as far as off roading is the steering these rigs need the crossover set up as they have no steering when the drivers side front gets drooped out.
When I set my M1028 up I was concerned about fuel capicity with the stock 20 gal tank but have had it out 2 solid days and it burned less than a half tank your not going to do that with a gasser.
I would shy away from the M1009s unless you have to have the cab room the pickups already have the HD axles and low gears.
For trail runnung & crawling the diesel will work great but its not for a high HP or high RPM application.
Mine is 4" ranchos in the front with a shackle flip in the rear running only the top 5 leaves. 37" tires, hyd winch (never used yet), shortened bed 14" between the wheels & taillights. Very capable rig that's hard to stop!
