This one didn't actually exist, but is more of an oh-so-nearly.
Anyway, was just casually reading about the old GT1 regs of the 90's and the how they came to be, along with the all the legendary cars, and how they developed, when I stumbled upon something new to me; Audi's then planned GT1 project.
Basically, Audi decided to get into GT racing, and get in on some of the fun that the likes of Merc and Porsche were enjoying. At the time however, the TT was Audi's only true sports car, and as a result it formed the basis for their GT project; code-named Aurora.
The initial proposal was to create a car eligible for the GT2 class, by using the TT as a base on which to create a race car. This GT2 machine would be called the G-TT, and was planned to vaguely resemble a TT, but generally look more dramatic and be mid-engined; unlike the TT, utilising a twin turbo V8 in the process.
Beyond creating a GT2-spec machine, Audi considered that that the next step would be to obviously turn this into a GT1 machine; with this part of the project evolving into the R8 GT1.
Looks like things got beyond the simple sketch stage, as Audi even created a smaller scale model of the design to use for wind tunnel testing, where they used the ex Brabham F1 team rolling road wind tunnel.
Either way, turns out things were pretty serious, as they reportedly conducted over 550 "runs" with well over 50 different variations of the original concept created.
Also, with this being a potential GT1 entry, there would have been the need to consider making a road car, and apparently Audi wanted to go down the route of creating a road car from the race car; much like Toyota and Merc did etc, instead of the other way round.
Spec wise the G-TT road car was designed to produce around 450bhp and be fully bespoke beast, whilst no specs seem to have been released about the proposed R8 GT1; though I'd imagine it would've been around 600bhp like the rest of the GT1 cars at the time.
The initial idea was reportedly summarised in late '96, with a view to eventually entering a GT1 eligible machine for the 1998 season. However the big bosses at Audi saw that the new LMP class was the way to go, so the original idea was set aside, and instead developed into the R8 LMP which we know now.