I have never (PERSONALLY) seen any but one problem with a 3in. I have ran one on ever truck I have ever had, and same with all my friends. The ones that I seen have problems were directly caused by bolts not being kept tight and the body moving around on the mounts. Causing cracked core supports and such. Alot of people complain about the gaps between the frame, yet they have hacked fenders and destroyed doors..... I love the gaps for ease of washing everything, tightening certain bolts, doing any work on the drivetrain, extra cheap lift.
We did my Suburban in my driveway, a pickup is even easier. Just do one at a time, and dont tighten anything down until they are all in, and you line the body lines back up.