It amazes me that the same players continually offer the same misrepresentations.
THE FACTS
The spindle used on 75-50 Granada/Monarch and 74-77 Maverick/Comet have IDENTICAL geometry to ALL 67-73 spindles originally used on MUSTANG. The Granada type spindle is orders of magnitude more available than any 67-73 Mustang spindle, and thus it is far easier and less expensive to find a decent set.
The Granada and 67-73 MUSTANG spindles have slightly different steering geometry than a 65-66 V8 spindle. This can cause problems with achieving proper wheel alignment. There are better solutions available for the V8 65-66 application, including new OE style spindle. The Granada spindle remains a very good and economical solution for converting 6 cylinder 65-66 cars to V8 spec disc brakes.
In addition, there are caliper and rotor upgrades available for the Granada spindle, including SN95 type aluminum dual piston calipers and thicker rotors.
I find it interesting that a few of the prolific and knowledgeable posters here will constantly MISREPRESENT these facts, obviously to serve their commercial interest.
In answer to the OP. The 74-77 Maverick disc brake system, including spindles is a DIRECT bolt on system that will yield OE spec suspension and steering configuration on your 68. The 68 Mustangs 14" wheels will not fit the Maverick rotor's hub unless the bearing housing is turned down to 2.44". Before someone decries that hazard of turning the hub housing, keep in mind that the 68-73 housing is 2.44" in diameter and is taller than a Granada's (thus is weaker than the Granada's). Use the tie rods from the Maverick.