Its quite easy to make any swingarm fit , its also easy to have some width machined off the sprocket carrier to help with chain alignment, there's usually plenty of room to do this, I've done it on a GSXR swingarm. The problem with stock monoshock swing arms is that they are all far too long, I have a GSXR1100 swingarm in a 750/4 {F1} frame , I had the monoshock section removed and the arm shortened, it was around 6 inches longer than stock, this completely changes the way the bike handles for the worse, it also defeats the purpose of putting a modern front on, A modern front end, if set up properly, will dramatically improve handling, whilst the extra long rear will slow down steering response at the rear and make the bike handle like a pig. I also have a gs1100 alloy arm, which is a twin shock arm, currently its around 3.5 inches too long, I'm having that shortened at the pivot end in the near future.. Just saying, if you want or expect the bike to handle as good or better than stock then what I've outlined here is whats needed, if you are just building it for looks then ignore what i've said, remember also, a longer swingarm also changes the wheels relation ship to the rear guard as well, so sometimes, no matter what you intend to do, there will be need for modification....