im not sure which year but the GT(4.6) switched over to the T3650
edit: read this it'll tell you about the differances http://www.mustangworld.com/ourpics/fcar/shift1.htm
Quoted from the site: In actuality (for conversation), the T45 in your 4.6L is a T5. It's just beefed up a bit more than the stock T5, so most shifters made for the T5 will work on your T45 (4.6L transmission). There are other differences between the T5 and T45, but for the most part they are very similar and the gear shift mount locations are in the exact same place. This Pro-5.0 kit will fit on any T5 or T45 transmission for '83 and up Mustangs. The aftermarket Tremec trans (like we have in our 5.0) uses a different shifter design.