The stock '68-'73 Mustang front disc brake setups were also of a single-floating caliper design. The '68-'73 Mustang single-floating caliper design was also produced by K/H. The '68-'73 Mustang disc spindles/brakes are
very close cousins to the '75-'80 Granada/Monarch front disc brakes. The '68-'73 Mustang disc spindles share the same splash shield and caliper anchor bracket mounting point dimensions as a Granada. --with the exception that the upper caliper anchor bracket mounting hole on a '68-'73 disc spindle is for a 9/16" bolt and the upper hole on a Granada spindle is for a 1/2" diameter bolt. All other critical mounting points and overall dimensions remain the same between the '70-'73 Mustang disc spindles and the '75-'80 Granada spindles.
'68/'69 Mustang disc brake spindles had thinner pins and smaller outer tie rods than the '70-'73 disc brake Mustangs. '75-'80 Granadas have spindles with the thicker pins and larger tie rod holes like the '70-'73 Mustang disc spindles.
In photo link below: On the left is a '73 Maverick drum brake spindle [same as '70-'73 Mustang drum brake spindle]. It features the larger spindle pin and larger outer tie rod hole. On the right: '75 Granada disc brake spindle. Same basic design as '68-'73 Mustang factory disc brake spindle except it too has the larger spindle pin and larger tie rod hole like a '70-'73 Mustang disc spindle.
'69 Boss 302s were the first to get the disc spindles [for the floating-caliper design] with the thicker pins and larger tie rod holes. Spindle pin and tie rod holes increased to the same larger dimension on regular-production Mustangs starting in 1970, --for both drum
and disc brake-equipped Mustangs.
The '75-'80 Granadas share the same front end width and
suspension geometry as the '67-'70 Mustangs. This is why Granada disc brake systems are a direct bolt-on to the '67-'70 Mustangs. They are not a
direct bolt-on, if using wrecking yard Granada spindles, to '65/'66 Mustangs, due to the '65/'66 Mustang's 2" narrower track width.
--The steering arm angles of the Granada spindles will be off for a '65/'66 Mustang. This would be the same problem you would encounter if trying to use '67-'73 Mustang spindles [disc or drum] on a '65/'66 Mustang. The problem for the steering arm angle can be made to work on the '65/'66 Mustangs by shortening the tie rod adjuster sleaves and shortening the threaded length on both the inner & outer tie rods on both sides, but steering arm angle would still not be
totally correct on a '65/'66.
However, there are [new] Granada spindle castings available to adapt Granada discs, to pre-'67 Mustangs, that have the correct steering arm geometry cast into them to alleviate the problem of trying to use incorrect-geometry wrecking yard Granada disc spindles on a '65/'66.
Recent installation of Granada discs I installed on a 6-cylinder [formerly 4-lug drum] '67 coupe.
Before:
After:
Stock '68-'73 Mustang floating-caliper front disc assemblies pictured below. Notice the similarities between these and the Granada disc brake system: