Yeah, the 06-08 trucks cannot run 305s without 1/4" spacers. Generally 285 is the widest that will fit without rubbing the UCA. 285 will fit fine though. Not too many people run the 285/60 because the BFGs and Duratracs are about the only options in that size I believe.
06-08 chrome clads w/33" Cooper Discoverer H/T Plus, Mopar tailgate spoiler, debadged door trim & tailgate emblems, 13" antenna, LED dome & maps, Magnaflow 22" SI/DO, 18% tint, "HEMI" hood spears, VHT tinted tails & third brake light, Lamin-x optic blue fogs, leveled w/McGaughys 2" drop shackles.