Get a Dyna that does not have the cross over opening. A Harley exhaust clamp is needed. You can pick these up cheaply at any Harley dealer. The clamps will run you about $10 each and the muffler anywhere from $20 - $50, (ask for a take-off). Then take the header pipe and the muffler to a exhaust shop and have them make you an extension pipe (about 6" long). This pipe can or can not have a slight bend, (about 5 - 7 degrees). I found that the bend was not necessary. But, I did flip my rear brake arm to keep the soot off it. (Be careful doing that). Then all you will need is an exhaust heat shield to neatly cover up the joints. You can also mount the exhaust pipe directly on the canister, if you don't mind the short lenght. A muffler off a 2004 Dyna will get you where you want to be.
Having done all of this, I then bought a Hard Chrome pipe off of Lancer, (great sound by the way), and used a piece of my extension pipe that I had made to act as a gasket.
Remember one thing if you do this - REJET your carb, or you WILL be running way too LEAN - not good. And you WILL blue up that nice shiny muffler you just put on. Don't ask me how I know.