Good luck getting someone to answer. I asked the same question on here with no help.
Easy guys, this site just went through some changes and the old "unanswered posts" option disappeared. I have found the members here quite helpful, but they do have day jobs and aren't always lurking around.
I only have a Z71 4x4, and no experience with other set ups, so I would not want to give you unsound advice.
You generally can't go too much bigger than stock size without adjusting your suspension, or you will get rubbing depending on what you buy. One of the internet tire sites has a comparative calculator that you can plug in combinations and see what is compatible for overall diameter.
For instance, I have a 265/75/15, and it says I can go 245/70/16, or even go 18" with 235, but I have to ensure the new rims will fit my truck and its brakes (ie aftermarket rims). By reducing tire size you hold your circumfrence within your limits.
Backspacing is another matter, and I think I've seen 4.55 as the benchmark here in the past (but don't go wih my opinion without confirming anything for yourself).
Just take your time comparing wheels and tires, and price out your options before spending your hard earned money.