How much horespower?
Depends a lot on what engine yours might have. The 5.0 L V-8 engines had in the area of 125-150 base hp, because of being so strangled by early emission controls. The 2.3L Turbo 4-cylinder (not sure if it was offered yet in 84) had slightly higher HP, but suffered from head gasket and other problems.
Search Ford Thunderbird Questions
Ford Thunderbird Experts