The harness from my 06
stang does work on the 08 GT seats with one slight mod.
The there is on connection on the consol side of the passanger seat where the harness wires do not line up, unless you shave off the lip on the female connector on the harness. After you shave of the plastic lip it plugs in an locks.
FYI just make sure the wire colors are in line with each other.
I did disconnect the battery while working and everything was fine when I reconnected.
Just make sure you get the harness from your old seats so that you will be able to plug and play with the new ones.