Hello Frank
I would not worry that some of the muffler has been trimmed off as long as the spring end is still intact , I have trimmed them off short for combat models.
Attached are some copes of the instructions for both the spring and baffle plate models, also added the instructions from a Tatone Peace Pipe as they are relevant too and a nice muffler if you can find them (my favorite aftermarket 'old' muffler).
Regards Gerald