Welcome to FYIFORD.

First, the TTII wheels may be a problem. Take your 13.2" brakes and slide a loaded caliper onto the rotor. Place the wheel face down on the floor and place the rotor/caliper assembly in the wheel. Loosely place some 1/2" bolts to center it in the wheel, like wheel studs.  Then you should be able to slide the caliper around the rotor to see if it clears the wheel spokes.

Use one of our PV-100 adjustable proportioning valves, as it will also work with four wheel discs later.

The PB-6.1 master cylinder is for disc/drum systems.  You can use it with four wheel discs, but it would be better to convert to the PB-6.2 which is a true disc/disc master.

The master cylinders are also listed on the same web page as the big brake kits.
Www.mustangsteve.com/cobrabrakes

1st post... I have just purchased the PB-2 kit and am about to begin the install. I have a question similar to OP above. I have the S197 GT front discs (12.5) installed, and already have the Explorer rear with discs but not installed yet. Mine is a '66 in the process of restomod assembly with a '93 5.0L HO and tremec TKO (yes I know the trans tunnel will need some relocating) and to confound the problems, I have the Borgeson power steering installed and I've purchased the McLeod hydraulic firewall clutch master cylinder (see design of clutch master: part number mcl-1431001 on summitracing - sorry, 1st post means I can't include a link yet). Also, I have stock hipo (k-code) exhaust manifolds with stock type exhaust pipes.
(Q1) The template for the firewall holes for PB-2 show the smaller vertical hole spacing on the driver's side, (but photos of the vacuum booster always show the closer spacing on the passenger side.) I don't have a booster yet (see below Q's) so trying to be cautious. Side note to Steve: the printout is 3/8 too small, good thing you noted the 5.50" measurement. Do you have a pdf I could d/l and reprint?
(Q2) I wonder if the 2.3L 4cyl brake booster I had planned to use will clear the McLeod clutch master cylinder since it slants down underneath the brake MC/booster? Or, does the 5.0L booster have a smaller diameter and be necessary to clear the clutch master?
(Q3) In my brake application, which master cylinder would be recommended with driver side outlets to clear the shock tower? My original plan was to use the Windstar MC as noted in an old 2013 post, but if there's a different recommendation should I need to use the 5.0 booster (or another booster like an OEM hydroboost to manage clutch clearance), what would be the best MC?

Last edited by dkrasniak (6/11/2017 7:51 PM)

MS, I'm about to install my GT 12.5 front and rear GT 11.75.  I'm wanting to use a Wilwood MC and can't decide on which size bore to use.
Will the same bore work for the GT12.5 and the Cobra calipers?
 

Use 15/16" or 1.0" MAX   The 1.0 is preferred when you install my power brake conversion.

1-1/8" will never work as you will never build enough line pressure.

If you want to use 14" wheels on your 68, you have two main optons to use oem Ford brakes.
1. Use brakes and spindles from a 68-73 Mustang. If using 68-69 disc spindles, they bolt right up with stock tie rods. If 70-73, use 70 Mustang outer tie rods.
2. Use brakes from a 75-80 Maverick, Granada, Monarch or Versailles.  They bolt up with correct geometry. Use tie rods from the car the brakes came on. They will fit the 68 adjusting sleeves. Versailles spindles have a larger lower ball joint hole, but that can be remedied using MustangSteve part #LBJ ball joint adapters.
A third option is to use the 67 Mustang discs, which would bolt to your existing spindles.

All of these require a proportioning valve and a disc-brake-specific master cylinder.

All factory disc brake equipped 68 Mustangs and Cougars also had a vacuum assist booster and a power-brake-specific brake pedal.  This setup is available as MS part # PB-6770.

You will also see other aftermarket kits like Scarebird that use Chevy calipers and other kits that use Chinese made parts. While any of these should work, in my opinion, using Ford brake parts is the way to go.