The 05-up GT's use the Tremec 3650 transmission.
.........T5...........3650
1st |3.35:1 | 3.38:1
2nd |1.93:1 | 2.00:1
3rd |1.33:1 | 1.32:1
4th |1.00:1 | 1.00:1
5th |0.68:1 | 0.68:1
Final |2.73:1 | 3.55:1
Also, the new mustang GT's don't have a slip yoke to connect the driveshaft to the tail shaft. I think the 3650 can handle more power too.