Ive seen one other slight fix rather than use shims or used with shims. Put the spring center pin in the forward most hole on the axle perch. You might have 3 holes per side or just the one, it depends upon the truck. This results with the axle rearward about an inch and you might have to drill out the ubolt flip plate. So rather than having moved the axle forward 2" with rears up front you only get an inch. I guess it depends on why you wanted rears up front: for the articulation, approach angle, or are you just greedy and want both? <img src="/forums/images/graemlins/smile.gif" alt="" />

My .02
JT