All Pro Flo header systems will marry existing SPC mufflers as long as they are both for the same bike. Example, if you have a Softail Big Bore, you MUST order Big Bore Pro Flo Headers. If you have an Elsinore system you MUST order Elsinore Pro Flo Headers etc..  You cannot swap Big Bore, Elsinore, or Turnpike headers if you do not already have that system. Any questions, pick up the phone and dial us *Due to slight variances where metal can contract or expand with heat, if you experience any issues with fitment we are happy to properly re-swage any headers to your muffler. We just require you to send them back in to us.