To offset or not to of set….. That seems to be the big question these days. The main issue here is wheel build strength. At first this seemed to be a major concern before hearing of the awful thrashing that Thor form Surly and Ruda from GBS put on the offsets and ultimately gave the thumbs up to.
Issue number two is hub availability. As of right now there are only a few 170mm hubs available. 135mm hubs are standard issue mountain bike spacing, so any 32h mountain bike hub will work on your Fatty.
In the front there are two options as well. Front brake or rear brake spaced. Salsa, Surly and 9:zero:7 all use rear brake spacing. White Brothers and most of the small frame builders use front brake spacing. We use the Paul WHUB front hub for these situations.