it's the same as in FIA GT since the fall of 90's... you can see all the results with the name of cars and specific classes here: http://www.lemans.org/24heuresdumans/chronos/h24.pdf
Porsche do not have car in GT1 now. in previous rules, the GT1 car was 911 GT1. in GT2 they run 997 GT3 RSR, which is a very different car to GT3 RS. As for now, Ferrari also runs only GT2 car - F430 GTC (430 Scuderia does not compete anywhere), which is made in two versions - GT2 and GT3 (which competes in FIA GT3 class). in GT1 they had 575 GTC and couple of 550 versions made by italtecnica, prodrive and weith, not ferrari itself