Hi Joe,
I'm not Sandy but I can answer your question.
The 911 model is internally known with a model designation of 997 for the current model year, both the GT2 and the GT3 were based on the 996 model as such they are not available in the 997 body style currently.
The 996GT2 was a 3.6 liter Twin Turbo with about 480HP stock IIRC, RWD using the same chassis as the 996TT (widebody) using a coil over suspension with adjustable height and adjustable sway bars and fixed wing.
The 996GT3 used the same egine as the 996GT2 or the 996TT, but it was a NA (No forced induction), RWD using a stiffened Carrera 2 chassis (narrowbody), it also used a coil over suspension with adjustable height settings and adjustable sway bars, the amount of sound insulation that was added to the GT3 was minimal, had a fixed rear wing and used the narrow body (Carrera 2) for better top end speed.
The GT3 was sold as a turn-key track car. There were actually 2 models of the 996GT3 that went into production a model commonly known as the MKI that was available everywhere else except the US with a very limited production run that was used to homologate the GT3RS race car that was run in the LeMans GT class, ALMS GTS class, GrandAm, etc, etc and the MKII which is the version that became available in the US with a more abundant production run, and there is another GT3 known as the GT3RS which was not available for the US market that was used to homologate the GT3RSR race car (it used a different front suspension geometry than the MKII GT3 and was also lighter and had more power than the MKII GT3)
The 996GT3 MKII was rated at 380HP, MKI's were rated at 360HP, GT3RS were rated at 425, but based on many dyno runs done by owners the MKII engine was *very* underrated by Porsche, depending on the car, some engines were really putting out anywhere from 400HP to 425HP at the crank.
And then there is the plain vanilla 996TT, using the same engine block as the one used on the GT2 (Twin Turbo) but using a 4WD chassis (widebody) with it's own specific non-adjustable suspension and lot's of creature comforts. (Not really a track car like the GT2 and the GT3).
Both the GT2 and the GT3 were available with either PCCB (Ceramic Brakes) or with regular brakes that were substantially larger than the 996TT.
The 996TT, GT2 and GT3 shared engines, the engines used dry sump lubrication built in and were based on the racing engine that was designed for the 996GT1 car (exotic car based on the GT1 racecar made by Porsche during the 1997-1998 model year) So they were really race engines that were put on street cars, very different from the engine on the rest of the 996 like the Carrera2, Carrera4 which used engines derived from the one used on the Boxster (thus the infamous RMS issues on the early model 996's as well as the Boxster, which the GT2/GT3/TT did not suffer from)
Hope that this clarifies things a bit. There is a lot of history on Porsche's so trying to keep track of which car is what can be a pain for those who are not familiar with them.
Ken
