i used to say just get any ole fix/fix track wheelset and screw a freewheel on. for a long time i'd never heard of anyone having problems with this setup, and i'd run it myself offroad without any troubles.

but recently we've done three warranty replacements for giant bowery wheels with this setup (they ship with a freewheel on a fix/fix hub stock). threads stripped clean off, i think it's a quando which are known for being kinda crappy anyway but thought i'd pass on the word.

so i guess i'd say get a true freewheel threading (at least on one side) if you can.