I am probably being very naïve here but I have bought a brand now downpipe ( stock ) and also a used ( but very good conditions ) silencer ( muffler ). Because of what I have read... I have assumed that nothing has changed in the dimensions of the stock savage exhaust system since the models incept until now. So I have assumed that my shiny new downpipe would fit into my slightly older muffler ( silencer ). It doesn't seem to however. Various diametres seem ok.. but when I marry up the downpipe AND the muffler the overall length seems to be about an inch too long. I may be doing something wrong but I can't see how. Is there anything that can tell me how these things go together and what the various dimensions should be please ?

Ditch that muffler, get a Dyna. Better looking, MUCH nicer sound, & its faster, immediately, cuz its lighter. Mite need to rejet, ehh,, but who cares? Itll run better, sound sexier & be prettier.. all for a whoppin 20 bucks..

Yes, the coupler gasket .

My Dyna was leaking so I put the stock muffler on for now.  I had more problems getting it off than n.  Putting it back on was a snap.  Try twisting and rocking it to get it to seal into the header.