I have one, and its got the 110mm hub, best way would be to find an old 110mm track hub, not common but they do exist. 2nd best way, cold set the dropouts to 120mm, not an ideal option but doable, although that 4130 cromo frame is pretty stout, aint gonna be real easy. 3rd and ugly option I dont really recommend but ive seen others get away with it, and thats screw on a fixed cog, followed by a BB lockring I think will fit on(maybe, 1.24" by 24tpi isnt it?) and lots of blue loctite.

If its got the newer hubs all you need to do is lace up a wheel with a ss/fixed hub, or have someone build you one.

Ive ridden someone else's fixed MTB, and it takes some getting used to, fat tires dont skid like skinny ones, and having a heavier bike to muscle around makes a difference. For off road fixed MTB is pretty insane, having to snap the cranks to horizontal all the time to clear obstacles can be tough sometimes, same as bunnyhopping a curb on a fixed just with a bigger and heavier bike plus dealing with bumpy terrain makes it quite challenging.