I thought the wheels were 0mm but I bought a 5th wheel/rim with 0mm and it doesn't match the rest of the wheels. I'm pretty sure the rims are 15x8 with -12mm offset. Having more offset has helped with getting the front wheels to fit while turning.
You dont need to extend the auto linkage, just adjust & its very easy. The transfer case shifter needs to be extended and there are a couple ways to do this.
I haven't re-geared yet & can still get up to 75mph on the highway pretty easily. I have a 12 bolt 3rd sitting in my garage with an ARB locker and 4.56 gearing that I'll install next spring along with a matching front 10 bolt.