If it's a dual-drive twin axle setup, pulling just one axle isn't going to be practical. the front axle has a "power divider" that splits the torque from front to rear, and can't work independently of the rear axle. The rear won't be heavy-duty enough to pull the truck by itself. You'd need to remove both axles, and replace them with a single-screw setup, plus rework the entire rear suspension and driveshaft system. You'd be better off buying a single rear axle truck, both from a reliability and a cost standpoint.
Jerry
