Back in the early 80's, I decided that when I finally decided to Restore my 67, I wanted to add Power Brakes. I thought that I would start trying to find parts so that when the time came, I would have everything, or at least most everything that I needed. At that time, I had the 1965-72 Master Parts Catalog, and tried to determine the major items that I would need. Those items turned out to be the Booster unit, a different Master Cylinder, a different Brake Pedal, and, according to the MPC, a different Pedal Support.
As I usually did back then, I started with my Ford Dealer to see what might still be available. To my surprise, the Pedal Support was still available, so I ordered it, and also got a Ford Rebuilt Master Cylinder, and a Power Brake Pedal Pad. Over the next couple of years, I found (through Hemmings - no internet back then) a NOS Booster. After that, I didn't actively pursue any additional parts for the 67, due to work and other projects. I drove the car off and on until the mid 90's. It then sat until about 10 years ago. By then, I had accumulated a lot more resources and knowledge about 67's. One of the things I had found out was that a different Pedal Support was only necessary if one had an "early" 67. Of course the question is, "what is early" ? I still don't know the answer to that. As it turns out, the "later" Pedal Supports actually had a knock-out for the upper holes used for the Power Brake Pedal. Therefore, all that is needed is to punch out the knock-outs and remove the captive cage nuts that were for the non-power Master Cylinder.
About 4 or 5 years ago, I started dismantling my January 31 build 67 for Restoration. I still haven't removed my pedal support, and can't really see if it has the knock-outs for the upper holes or not. However, since I have the correct Power Brake Pedal support, I am "good" in any case.
In regard to the pedals themselves, something that I hadn't picked up prior to dismantling, I thought that it was time to "attack that. It bothered me that, over the years (and still today), I had seen many listings that noted "Power Brake Pedal, 1967-69", and even "1967-70 Mustang Power Brake Pedal". My concern was that the Ford Parts Books show that each year had it own Part Number, signifying that there was "something" different with each year. I figured that it was time to dig into this in depth. I finally found "Mustang Steve's" site, which had a great write up with pictures, about Mustang Brake Pedals. I have attached a few pictures "borrowed" from his site. Bottom line is, first, the Power Disc and Power Drum Pedals are the same ; and secondly, the 1968-69 Power Brake Pedals, although not technically correct, will work, but may need a slight modification (in terms of the notch), and will have more offset than the 1967 Pedal.
The other great thing I found was that a friend happened to have an original Kit for converting to Power Brakes, with the original Instructions, which he shared with me, and I am passing on here.
Hopefully, this will help, and take some of the "Mystery" out of this relatively simple, and straight-forward conversion - assuming you can come up with the correct parts of course.
Bob