There were two Fleetwoods at Cadillac for a while. When GM downsized and switched the RWD C Bodies to FWD C Bodies in spring 1984, Cadillac had Fleetwood and the Fleetwood Brougham. Fleetwood Brougham became Cadillac Brougham in 1987. The FWD Fleetwood was still a C Body, but sharing looks and parts with Deville with more features and options. This was until the Fleetwoood name was put on the B Body (D Body)Cadillac in 1993. That FWD Fleetwood became Sixty Special in 1993. Then in 1994 you had the FWD Deville that was placed on the FWD K Body platform shared with Eldrorado and Seville. Then the C Body was dropped after 1996. The B Body platform(Roadmaster,Caprice,Fleetwood) was dropped after 1996 in favor of suv's and trucks. The 1996 model year was the last year for the C Body because the Ninety Eight was dropped and replaced with the H Body "Regency" and Park Avenue went over to the G Car platform in 1997. Regency ran for two years(97-98) and then the Ninety Eight trim was used on the 50th Anniversary Edition of the Eighty Eight. The Seville switched over to the G Car in 1998. Eldorado died a few years after that. Then 1999 was the last year or the H body Eighty Eight, LeSabre and Bonneville. The Bonneville and LeSabre went over the G body platform. Eighty Eight was dropped the same year the Cutlass name was after the 1999 model year.
The G Body was used all on GM luxury and fullsized offerings. The Aurora was dropped after 2003 model year.The Seville switched to RWD on the sigma platform. The Deville is on the updated G platform with the Buick Lucerne for 2006. Park Avenue and LeSabre and Bonneville were all dropped as of fall 2005.
Rumor has it GM is working on a Zeta rear drive platform program they dropped and brought back. It is supposed to spawn Chevrloets, Pontiacs, and Buicks.
*** A side note, Oldsmobile before its demise was pushing GM for a sigma based Aurora.