5 or 6. And half of them are on the 14.5" barrels pinned and welded.
I don't know of any companies making mounts for surefire cans. "Generally", the suppressor company will make the adapter for another company's mount. Dead Air is the manufacturer of the part that threads into a SilencerCo Omega to use Dead Air brakes on SilencerCo cans.
I don't know of any such adapter, Quiet Riot for sure will know.
Surefire also came out with the Warden you can attach to any of their socom muzzle devices