The Manitou Mastodon Pro version is an incredibly nice fork. The damper part is great with adjustable fast and slow shock absorbers and rebound adjuster. The air spring also has pretty nifty adjustment in the IVA and you can get the infinitely adjustable IRT for maximum controllability.

If you want a shorter axle to crown you can choose the STD model but that won't fit the largest tires. The EXT fits all current fatbike tires but has longer axle to crown.

You really may want to consider the mastodon over a 29er suspension fork. It's more fork than most will ever need.