Our CO shop just completed another DeWeldtec, here are some of my thoughts on the 2wd lift stuff:
Justin sums it up well in the video, 2wd lifts aren't a replacement for the traction of 4wd (or an improvement in handling) especially under an RV. The speed you need to carry to keep momentum in a situation that needs 4wd is just too high for an RV or most camper vans. Our custom spec'd springs under our 4x4 conversion are a major overall improvement to any E series. We don't use an off the shelf spring and then compensate with the shocks, our combination of spring specs, steering angles, shocks and sway bars are the way to go.
The beaches and ski slopes these rigs enjoy need 4wd.
I get a lot of inquiries about these 2wd lifts and what can be re used if they decide to go 4wd in the future and the answer is simple.... Basically nothing! Rear springs if you opt for that if they're spec'd properly by a competent builder. A "lift" isn't the same as a 4x4 conversion because the "lift" maintains the stock or modified I-beams and radius arms. Our suspension is a complete replacement.
So, as I've said for many many years. Do it nice or do it twice!