Cool - thanks guys!
I have a vintage Russian folding bike from the 50's and the rear wheel is in pretty bad shape (and my 260 pound frame isn't helping it much!). The wheels are 20" so it doesn't seem to be a problem swapping them out.
I actually found a 48 spoke rim with a coaster brake on ebay - it's on the way
Hopefully I can sell the other rim (which seems to be in really good condition) or perhaps convert it to a fixed wheel. I didn't think about the spacing - hopefully it won't be a problem that a different sized nut couldn't fix
Could you point me in the direction of the fixed cog conversions? I've done some google searches but don't know if what I've come up with will do the job.
Thanks again!