do all 97+ GP GT's have the 4T65E trans?

Not sure which trans I have. I have a 98 GP GT. I would like to get the Thrasher shift kit for a firmer shift. Any owners of non GTP cars have this kit installed?

Give me your VIN number and I will try to look it up for you.

I thought GT's had the 4T65E, and the GTP's had the 4T65E-HD?

GTP Girl is absolutely right! here is the email information I received back from Thrasher products:

Actually the GT's have the 4T65E trans as well, but the GTP's have
the HD version of the same trans. The shift kit will work for either
one.

As for the settings, there are 3 different ones. There is the mild, an
intermediate, and the "bang-screech" setting. Most of our
customers that are using the shift kit in their everyday driver usually
goes with the intermediate setting.

That is the norm. I would not hurt to double check with the VIN number. No 98 was supposed to have 3.29 OEM final gear ratios but mine had. So it would not hurt to double check