ah! I bought a shimano 16T freewheel, I've read mixed reviews but hopefully she holds up. Did you have to use the tensioner because of the 17T or did the 16T without a tensioner end up not working out?
Hey man! Great looking bike!
I know this is an old post, but I just wanted to let you know that you inspired me to do this same conversion to an old SM400 I had lying around!
It should serve me well, as a quick low maintenance way to get around town!