By the looks of things, with a little bit of fabrication to your frame, you could run a monoshock with the swing arm. I wonder what kind of bike this is off of?
I don't think it was off another bike, The mount close to the pivot is the mount for the brake stay not a monoshock mount. The arm looks like it was made to be a twin shocker. If it is off another bike it would have to be one from the early 80's since bikes went monoshock around that time.
Looking at it again it could be an early gsxr swingarm that was heavily modified (the rear axle adjusters chopped and replaced with those thicker ones. Auction ends on christmas eve, wonder who is gonna be looking at it then <loads sniper rifle>