The Audi R10 ran wastegate turbos as well, as Garrett was only just developing VTGs for racing diesels.
Of course, the Taurus diesel used the 5.0 V10 TDI out of the Volkswagen Toureg/Pheaton, and with no factory support from VW.
www.mulsannescorner.com is a good place to start to find the ACO's regs, and IMSA and the ACO's offical sites have PDF files of their sporting and technical regs, too.