I want to add about the "glitch".
1. the 930 Turbo can be glitched. I also believe that the Z can be also.
2. And most important. I really don't see any advantage to it. It just like an alternate build path.
When you remove the SC on the GT, you can push it back up to A600 with light weight and grip and make a really good grip car out of it. The problem is the the now famous AWD swap stigma attached to the car. Do them both and times will plummet for short tracks.
The reason I see no advantage is because of the Turbo. If you glitch that one and put it down in D Class. Its a real dog. Between the lack of turbo and now in comparison rather large weight, and add the fact that the stock gearbox is a really wide four speed, it won't go at all. I have to use the race gearbox to keep the revs up in my C Class grip build. Which is rather nasty BTW.
I think right now my C4 GS Vette is my best overall car. Tires, aero, and the heavy adjustable parts. Nothing else. But its so forgivable with the tall sidewall tires, you can get away with it. And because its one of the aero cheater cars (Vettes, Ferraris, NSXs, Most MR cars) the top end is really good for the power.