Putting the 17" rim on the Special
by Steve GammonThe change of rear wheel is possible as I have done it to my '79 SF. If you do this make sure that you get all hardware involved, e.g., spacers, bracket to hold the caliper, etc. I had to mix and match to get everything to line up and unfortunately I do not remember which I used.
However, I am not sure this change is worth the pain. As Phil Stewart has mentioned, the size difference is not great and could be accomplished by varying tire size. When I made the change-over I already had a rim and a good tire from a parts bike.