Single speed Freeheel MTB wheels can be built , the bars and stem can be replaced .
the part that may be a challenge for the less Mechanical is getting the crank and hub end of the chain in a suitable alignment.
then spindle lengths of BB need be chosen , and that is not something to be sorted out from this end of the game .
if you have a bunch of different BB spindles you can try them , yourself.
if the frame is vertical dropout the chain cannot be tightened , you need a separate tensioner ..
I canot see the drive side you sent a NDS picture.
a fixed one will make the chain bouncing off less likely , it may be coming off if you use an old RD as the tensioner .
(but that is cheaper)
Last edited by fietsbob; 09-20-15 at 01:00 PM.