Alright, all you NEED is a tape meas. or a good guess if you aren't too particular, a sawzall, a drill and a rivet gun(with rivets of course).
Measure two inches from the end of the hanger bracket and I mean the two tabs that stick out. Then hack it off. Now I truly recomend a good chop saw or a metal band saw but that's only from the experience of doing it the way I did. Now drill the rivets out of the end cap. this part gets a bit sticky as the end cap has to be somewhat forcibly pushed inside the muffler casing. now you can measure and mark out the rivet holes for the end cap to use the originals but I just drilled my own where I wanted them. Once drilled pop in your rivets and you can bolt it on. I do suggest hitting the edges of the casing with a file or emory cloth or something prior to installing your end cap though just to remove any edges or burrs. You may also want to spray some high heat paint as you will have exposed metal.
In the end, I love it, it sounds like some of the older four-cyl. race cars like the old spitfires and such with a good build.