Go with the RC kit but you will have to get a 1.5" spacer if your going to use the 5100's .
since the truck is a pro4x and an 08 the coilbuckets are higher on the frame, and the 4x4 has the truck sitting a little higher anyways. using 3 or 2.5 spacer obviously lifts the truck, but the bilsteins also lift the truck about .5 even on the lowest setting, so the ucas are gonna be riding on the coilbucket. very recently someone did this and showed a picture of the ucas on the bucket, it was pretty bad. and there are actual lift kits that run you over 1000 dollars for 4+ inches. 2wd is easier cause all you gotta do is get a spindle and spacer, but we cant cause than the differential will get fubar'd. This is my understanding of it, hopefully someone else will say somethin. check out prgproducts.com too.is there a better setup to get closer to 4" WITH OUT running the 5100's ? and I am still new to the lift thing, what is the problem with running the 5100's with the RC 3" or 2.5" spacer i should say