Mastangs use T5s likes cossies.
Mustangs also use drag autoboxes (with cool stuff like transbrakes )
Mustangs with the above boxes are often turbod and push out well above 1000bhp.

Methinks you go to http://www.turbomustangs.com/forums/

American guy near me whos got some mad ford turbo V8 stuff said the bex he uses cost him around 400quid IIRC and is good for 1000bhp...