My HD was a PO addition, so I do not know what kind or model it is. The muff diameter is smaller than the header, and fits into it.
I've had to make my own attachment for the back portion screw that attaches to the bike (a funky bolted thing), and right now that is mainly what holds it on. If that came off, the pipe would fall off (and it HAS once on an exit ramp during rush hour traffic - urg.)
The clamp holding the muff to the header pipe is a circle clamp with a thumb screw turner (yeah, there is probably a tech term for this, but heck if I know what). I have used lock-tite. It works for holding the pipe about a week longer than when I don't use it.
Oh yes - see this little non-photo? Well tomorrow Photoshop is due to arrive in my hands. I may soon be back to posting photos once again...