06murder

my cousin and I been trying to set up my gears in my 06 Silverado, and its been kicking our asses! when we first took out the pinion bearing, big bearing pressed on look werd to us, it was like .035 or something bigger then the one in the kit I bought. what id the best shim to start with? we try bearing in kit with .020 shim and .30ish shim everything we tried it will make noise no matter what! we even try to set of gears 4.56( oh they was fun,lol) made noise but not as much as the 3.73 we tried. cousin thinks the pinion is good and it backlash problem, is there a place I can get some stock shims? we got backlash to tight going in and broke one.