69 Mach1 Drum to disc

won't work, the MK IV uses the big car/truck 5x5 bolt pattern, the stang uses a 5x4.5 bolt pattern. also the MK IV uses the very odd 9 3/8" rearend instead of the 9". you can use a 9" carrier in the 9 3/8" housing but it's more trouble than it's worth, especially because of the bolt pattern. the 9 3/8" rear also only has a few gear ratio's available and none better than like a 3.08 i believe they all used 31 spline axles though, which is probably the only good thing about performance wise. they will last forever though. my old 73 galaxie 500 had the even more oddball 9 1/4" eaton rearend, with the integral carrier and removable rear inspestion cover, sort like a 12 bolt rear.