P&G obviously. Also the SGT, SRF, MMM V8 Supercars, 2003 F3 Euroseries, and Saleen SE Cup.
As for GT, I hated having to decide which GT mod to use for any particular race - BPR, '97 FIA GT, default '03 and '04 cars, Spanish GT, Brazilian GT, Spanish GT, Italian GT, European GT, etc. All use a similar assortment of Porsches, Ferraris, Corvettes, etc. (plus McLarens and Venturris from BPR) so I merged them all into one big GT series. Drove one of each type at a couple of test tracks, tabulated my lap times, and created GT1, GT2, and GT3 classes based solely on performance (regardless of engine, production based or purpose built car). Removed duplicates and "ugly" cars (purely subjective). A few SGT cars may appear in GT2 or GT3 races, a couple of V8 Supercars may appear in GT3.
Also merged several Porsche Cup mods into one, drove one of each to decide which chassis/engine I liked best and used that for all.