It has an 8 tooth drive gear from the factory. This means that you have to pull the tailshaft housing and swap in a 7 tooth to do it correctly. The white driven gear that a lot of places sell is a hack fix, and based on feedback from people who have used them - it's not a good idea! Do some searches in the forums and you'll find some great pictures of them with the teeth all sheared off.
The only alternative is one of the electronic boxes (frequency to frequency converter), but they're a bit pricedy and mix reviews on durability.
AWESOME! That is exactly what I needed to know. I have to replace the tailshaft housing due to it's cracked so I want to put the right gear in while I'm in there.
You are the forth or fith person that told me to stay clear!!
I stalked to Stan at T5Atlanta.com where I purchased the tailhousing and he has been teriffic with helping me out. He also mentioned about the gear needs to be changed if swaping gears.
Parts were ordered from latemodelrestoration.com so I can get this damn stang on the road!