Will a disc brake setup from a 72 Mustang fit a 67? Also, will the rear end swap or is there a diff.?

 

theres a difference in sizes, some had 8 inch 8.8 and 9 inch differentals

 

About the rear end... the '67 mustang has a 59.25" wide rear end... the '72 has a 61.25" rear end. So it's about 2 inches wider (1" on each side)
If your wheels arent that wide, or have the right backspacing, it wouldn't be a problem, although the spring perches might be off by a little bit
Also are you switching gear diameters? (7.25-8-9) Because you might have to have your driveshaft shortened (or lengthened... if you're going from 7.25 to an 8)

http://www.dfwmotorsport.com/fairlane/9inchrearends.htm

 

Thanks for the help. Now I'm thinking about restoring and selling the 72, then I would have more money to put my other cars together. My mind twists way to fast!