Instead of getting the surly fixxer I would just buy a disc rear wheel and use a bolt on cog(tomicog or londonfixiebike) they should give you a 52mm chainline or so which should line up with your outer position of the current crank.

Also with large tires (2" or so) the gear ratios end up being pretty similar to what you would use on a 700x23. on my converted MTB I ran a 44x17 and that worked pretty well for me(I live in a really flat town)