This page shows the difference between the pre-MK3 Roadster muffler mounting brackets and the MK3 muffler brackets.

In order to convert a MK3 Black Cap exhaust system to a Pea Shooter exhaust system, you must install the pre-MK3 muffler mounting brackets. In this first picture the pre-MK3 muffler brackets are mounted to the shiny drilled Z brackets and the MK3 mounting brackets are mounted to the plain Z bracket. The Muffler mounting holes are the same distance apart for both type mufflers, but the MK3 Mufflers have the mounting lugs attached farther back towards the rear of the bike. If you would superimpose the two mounting systems on top of each other, the forward mounting hole (labeled B) on the pre-MK3 system would be on top of the top rubber mount (labeled A) on the MK3 system. All the other parts (i.e., foot pegs, nuts, bolts, spacer, etc.) are the same for both systems.