I was just comparing prices to local place and found this under thunderbird break booster, might be worthing contacting them about the car.
http://www.ebay.com/itm/83-84-85-86-87-88-FORD-THUNDERBIRD-POWER-BRAKE-BOOSTER-/200728543775?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1983%7CMake%3AFord%7CModel%3AThunderbird&hash=item2ebc5a821f&vxp=mtr#ht_2541wt_992