Wayne is right. If the car you are looking at is a 1982 model year, then it is either a GT5 or a GTS. The GTS was produced concurrently with both the GT5 and then GT5-S Panteras. Production transitioned from the GT5 to the GT5-S in 1985 with chassis #9374 being the last of the GT5 production run (though not the last produced) and #9375 being the first GT5-S. The last GT5-S was #9562 which was built in 1990.
What is the chassis number of your car? Perhaps I have a listing for it and can give you some information.
The GT5 and the GT5-S were identical mechanically and in the interior. The only differences were in the body; the GT5 had fiberglass wheel flares, air dam and running boards, while the GT5-S had all-steel fenders with no running boards. The GTS had more narrow wheels and tires but the interior and, as far as I know, the mechanicals were the same as well.
I would recommend you purchase one of the good introductory books about the DeTomaso marque to familiarize yourself with the cars and their interesting histories. "DeTomaso: The Man and The Machines" by Wallace Alfred Wyss or the "Pantera Buyer's Guide" by Rob de la Rive Box and Matthew L. Stone would be the two I would suggest. There is also a new book just out by David & Linda Adler and Wallace Wyss called "DeTomaso Pantera" which, although I do not yet have it myself, I'm sure will be a very good introduction to the marque as well. You can buy it on the PI web site: http://www.panteracars.com/books10.html
Here is a photo of a 1987 GTS, for your reference.