I'm guessing that was a typo, what's the master cylinder bore size? 

The '93 Cobra used a 1" bore master with 4 wheel power discs.  That's what I run in my '89 GT with SN95 Cobra brakes (13" front/11.65" rear).  Both the booster and master for the '93 Cobra are still readily available from the aftermarket.

Now, what I'm not sure about is the 13" front/13" rear setup.  Typically the rears are smaller than the fronts because the front does more of the braking due to the car's weight bias.  You have to have traction to brake, and traction to a degree is dependent on weight.  I've seen cars with massive rear tires and small front tires run the same size or larger brakes on the rear because the tire's contact patch makes up for the traction disparity based on weight alone, but that was kind of an oddball case where a car basically had slicks and skinnys on it.  I'd be sure to have an adjustable proportioning valve, because I see such a setup needing tuning to avoid premature rear brake lockup under hard braking.