Your 67 Cougar will be very similar to my 68 Mustang, and I have MS's 08-10 brakes on it and it is lowered 1.5  inches. I have two thoughts:

First, it is all about getting the right back spacing, I have 17x8's up front and 17x9.5's in the rear, 245's front and 275's rear. My front backspacing is 4.75", my rear is different due to a narrowed 8.8 swap.

Second, do lots of measuring, and remember these cars are different from one to the next, even the same year and model, when you start trying to use every inch there is,an 1/8" can make a big difference. I have learned the hard way, that a tire that NEVER rubs and is one or two sizes smaller is MUCH better than one that only rubs once, but is bigger. Every time i make a hard left turn up a hill (like my drive way) my right front tire rubs, and one size smaller tire would have fixed that, or a 7" wide wheel.

Good luck, take your time, take lots of measurements (remember to take them with the suspension compressed, NOT hangging down), it will pay off in the end. I am going through the same process for my 73 Mach 1.