Get it to a diesel mechanic, but if you can’t check the fuel pump.

First thing you should do is check your owner’s manual for any advice Nissan offers for when towing. Patrols had problems with fifth gear, so you need to be a little easy on the gear. Use fifth, but don’t let the engine lug down too far, change down before the engine and driveline become stressed. I would think 2000 revs is a pretty good downchange speed.

HAVE you thought about repairing the chassis? Cracking is not necessarily the end of the world. I'd check with a chassis specialist who can inspect the cracking and determine if it's worth repairing. If you are intent on fitting the body to another vehicle it comes down to the weight of the camper body. Think about the weight when it's fully laden with all the gear you plan to take with you. The vehicles you're thinking of are nominally one-tonne utes, so they should do the job providing your camper is one tonne or less when full of gear.