If you are asking what trans will bolt up...A T45 from a 4.6 mustang will physically bolt to the 4.6 T-Bird motor but you are on your own trying to get the clutch actuation(Stang uses a cable and the T-Bird SC pedals and SC trans use a Hyd. unit) and shifter fabricated.
There is no way you are going to "Bolt In" any 5 speed trans in a 4.6 Bird. Any way you look at it you are looking at a lot of custom fabrication....Best of luck to you.