If it was me (and it is basically as this is what I did) I'd get an Echo TR fixed rear hub, trialtech 15t screw on sprocket, echo SL front freewheel, whatever bashring takes your fancy, and then try and pick up some 2nd hand cranks off here.
If you were to buy cranks new as well then get some trialtech sport forged 175mm and an ISIS bottom bracket if you haven't already got one fitted.