Lock_Cracker wrote:...I should have asked if there was a recource comparing motise cylinders and components of differant manufacturers. ... will any interchangeable core fit any housing? ...
Mortise cylinders and interchangeable cores are two different things. Mortise cylinders have a standard diameter and thread pitch (1 1/8" diameter - 32 TPI), but come in different lengths for different door thicknesses and, as others have pointed out, they take different cams depending on the lock being operated. The door must be opened, a plate removed, and a set screw backed out to remove one of these for re-keying.
Interchangeable cores use a special control key to remove the core without having to open the door or backing out any set screw. BEST is the most popular for small format IC's, and a number of manufacturers (Schlage, Yale, etc.) have their own designs for large format IC's. The benefit of interchangeable cores is that a building can be rekeyed quickly, so long as they have the control keys and documentation.
Pages 8 - 11 of this catalog from Ilco shows mortise cylinders and cams:
http://www.ilco.us/media/1407870/v3/File/cylinders-storefront-door-hardware-exit-devices.pdf Pages 20 - 23 in that document shows a couple of different interchangeable cores, in this case Ilco makes after-market cores for BEST (small) and Schlage (one type of large). There are many other proprietary interchangeable cores out there--books have been written on the subject.