Those are nice looking (style wise) mufflers, I wish I would have snagged a pair that went quite reasonable on e-Bay a while back...

You are missing the clams that secure the mufflers to the headpipes and two exhaust "hangers". They slip around the headpipes and are secured by the rear engine mountbolts. The mounts on the mufflers are totally different but looking at them maybe they are attached to the holes that the passenger pegs normally bolt through?
This pic shows the r/h side where the hanger attaches. The mounting on the l/h side is identical but all of our bikes have Brown sidestands which relocates the exhaust hanger on that side hence my picture of the right side instead...