@88foxconvertible
Here's what worked well for me.
Stock booster
I used a 94-95 Mustang master cylinder. Note that rebuilt 94-95 Mustang master cylinders do not come with a reservoir. That means a trip to the junkyard and some more money spent.
Your brake pedal may be very hard and almost impossible to lock up the brakes. I had to replace the front calipers with 73 mm calipers from a 91 Lincoln Mark 7 to get the braking performance up to par.
Other small parts needed to complete the job...
Brake line Adapter fittings for rear brake line
3 line to 2 line brake fitting kit
Proportioning valve, Wildwood 260-8419 Summit or Jegs
Kit to gut the stock proportioning valve Ford Racing M-2450-A Summit or Jegs
Emergency brake cable parts: Summit or Jegs or Late Model Restoration
79-92 Mustangs use: M-2809-A* Parking Brake Cable (need 2)
93 Mustangs: use 93 Cobra Ebrake cables.
All years use: M-2810-A* Parking Brake Cable (short cable that attaches to the parking brake handle)