We generally don't install stabilizers but we have if the PS system is an overachiever. Stabilizer adds some resistance. This van was a customer install so he installed it there. Some people think you need them, most actually don't. If our leaf kit gets DW its because something is really really worn out! Steering ends, leaf spring bushings, etc. Its not common like the coil vans that generally have at least one stabilizer.
Weight on the motor homes is all over the place depending on the size/etc. This minnie winnie was spec'd to 12k total, will have too dig up the actual weight before the swap. Our conversion adds ~600lbs w/o the goodies (winch, bumper, OBA, etc)