The Mustang front clip doesn't fit a T-Bird correctly.The cowl is totally different than the Stang.As far as the 5 speed swap,everything from the Stang is a direct bolt on swap except for a couple of parts.The floor gasket seal that fits around the shifter is different from a T-Bird to a Mustang,but,a Stang piece is easier to find and can me made to work very easily.The console panel for a 5 speed is different as well.You'll also have to swap brake boosters if you want to use a firewall adjuster for the clutch cable.The stock crossmember (double hump style on my '88) tranny mount and driveshaft were a direct swap from the AOD to the T-5.I did the Mass Air conversion a couple of years ago.Took about an hour.Pretty easy.Move two wires,add two wires,splice two wires on the computer plug in the kick panel.There are many threads with the details.I used Mustang instructions and followed them to a 'T' and everything worked as it should.If you're using a stock H.O cam from a Stang,Mass Air really isn't worth doing,but if you plan on more cam and more mods,then yes,Mass Air is good.A basic H.O upgrade makes a huge difference in these cars.

85 thunderbird 5.0