For the front I almost used the factory adapters from the 4x4. They would have worked, but would have made servicing the bearings a real pain. So, I bought the correct 2wd 3500 assemblys and bolted them on. Kinda sucks, because I just bought new front rotors a few months ago! Anyone want to buy a set of barely used 2500 rotors :D
One observation I made was that the 3500 rotors are near 1/4 thicker than 2500 rotors. They fit fine with no binding , but with new pads the sliders are almost maxed out.