If it was me, and I was going to do any serious towing or hauling I would go with a parallel style 4-link with panhard bar or a true triangulated 4 link where there are 2 separate upper bars that angle from the axle to the frame. A "wishbone" upper I don't feel will offer enough side to side support under a heavy load, you will most likely feel the rear "walk" from side to side as the single connection at the point of the wishbone is trying to keep the axle centered. Other than that yes, definitely have the supply separated going to each air spring and use good quality shocks. We've towed trailers here for many hundreds of thousands of miles with out fail. They ride great loaded or unloaded, plus since you can raise and lower the rear it makes hooking up a trailer much easier on the arms. Not so much cranking up and down
