here is a question I haven't found an answer too. ... I have a t5 and 3rd gear and the cluster gear are wasted.. my buddy has a t5 out of a camaro with the twisted shifter tailhousing... are the tranny's the same can I switch out the tailshaft housing and throw it in my car...???
You'll have to change out the tailhousing and swap the mainshaft. Since the gearing is different, that implies transferring the entire guts of the camaro trans over to the Mustang case while using the Mustang mainshaft and tailhousing.
Just buy a new cluster and 3rd gear off ebay. They are fairly cheap. Or if you have an 89-older t5 with the 265 ft-lbs rating, you can upgrade your trans