Just an update. For anybody with a 660 wanting a cheap upgrade or needing a new rear shock.
I bought a used 02 Raptor 660 recently and did this mod with a 2016 Raptor 700 SE rear shock. The brand new shock was only about $140 shipped to my door. Part no. B46-F2200-00-00
I did exactly what skull660 did. I drilled the "Elka" hole using his measurements in a used 700 rear link, used my 660 dogbone and mounted the shock. Only problem I had was I had to cut out some of the skid plate for the linkage to clear. Works awesome!!!