Sorry for the late replys, I have been out of town.
did you put any airbags in the rear or anything in it?
No, I thought i was going to have to. But when I put the load (8500lbs) of the trailer on the van without the weight distribution hitch on it barely moved (that is compared to my F150 with an GAWR rear of 3800), so I tried without airbags and with the WD hitch for a couple trips and it has worked out great. My F150 would squat a lot w/o the WD hitch and with the WD hitch the ride was very squishy and bouncy, so I installed airbags to stiffen up the rear suspension. So far the NV has felt great towing and I don't feel the need to install airbags.
KMGLTZ, How badly has it impacted your MPG? Any other downside to doing this? Is it louder? Is the ride more rough?
Truthfully I don't know, I bought the van new with the conversion already done, so as far as comparing non 4x4 to 4x4 i don't have any idea. I don't hear anything related to the conversion making noise so I am assuming that the noise in the cabin is the same. Miliage I get about 14-16 going back and forth to work, mostly highway, if I get stuck dropping kids off and picking them up about 12, mostly city, and If I am towing my TT (8500lbs) I get about 8-9.