You can search on "savage muffler" on eBay motors to see the kits.  The Harley Dyna muffler won't fit snugly, so you'll have to make your own sleeve out of aluminum can strips or something to take up the space.  You may encounter a shotgun backfire upon shutdown after the conversion, and there's a lot of advice here about minimizing it.

Yeah, I just looked in the tech section and saw where the pics are missing from the thread.  Someone will be along shortly to give you the deets.  I had one on mine but had to fab a mounting bracket whereas some on here mention getting a particular muffler that is a direct or nearly direct bolt on.  

BTW, anyone now how I can add my exhaust sound file to the Tech Sections TOC sound files thread.  I was just listening to them and mine doesn't sound anything like those.  I know they are pretty accurate sound files cause the stock sounded like my stock and the sportster file sounded like my sportster muffler.  I had gotten used to my new exhaust and guess I forgot just how different it sounds.

Do like Ed said.  The sporty muffler is a hollow tube with a single piece of metal in the middle dividing the length into two halves.  It makes the exhaust have to go around the metal piece through the perforated metal that makes up the tube.  Don't knock it out like I did on one of mine.  It's simply loud but doesn't sound very good, in my opinion, compared to other options.  Drill like Ed said.

I just wanted to chime in here real quick.  I have a sporty muffle on my bike, I got it used so the muffler came with it.

There is a reducer that connects the header to the muffler.  I recently replaced the header with a used header from a member here (THANKS AGAIN!) and when I did I noticed the numb nut did not have the reducer sealed on each end and the clamps were not the right size.  No wonder it was popping like a son of a gun on decel.

So when I put the new header on I lubed the reducer and slammed it tight inside the muffler and clamped it down so there would be a good seal.  For the other end the reducer was a tiny hair to big preventing a good seal.  This is no doubt do to the difference in metric ande standard pipes.  It couldnt mount flush to the stopper because then the muffler angle would rub against the rear brake cable.

So what I did was grab some muffler tape from the auto store, wrapped it around the base of the header twice.  Slid the reducer on to the best angle but made sure the tape created a "seal" inside it.  Clamped it down, ran it for 20 minutes and now everything is sealed up making the popping GREATLY reduced, no more exhaust leaks, and all I need to do is rejet for the perfect setup.