A sub-2000 pound GT40 that would be used as a street with some track fun days is IMHO a pipe dream. My GTD is pretty much a standard car and it weighs close to 2600 pounds full of fuel. To take 600 pounds out, it would in reality require a complete replacement of just about the entire car's chosen materials. Even then 2000 pound might be a "bridge too far"
The wheels/ tires alone would need to be close to 1/2 the weight of normal aluminum wheels/ street tires used on these cars. Think 10 times, or more, for the cost of Carbon disks over the steel ones we all are using. A glass windshield would be out of the question and you would be saving what, 25-30 pounds with a thin Lexan one. The only steel in the car would be the cylinder liners, crank, cam, grbx gears and shafts as well as a few more such as bearings and stub axels. Everything else would need to be light alloys and I'm not just talking simply a lot of aluminum. God only knows what a one-off racecar quality carbon body would cost? 10s of thousands would be my guess.
I could go on and on but just think a 25% or more reduction in weight for every single piece on the car! Where would you source these parts? It could be done with no budget and max dollars but you would need to spend at least 10 times the money of a "standard" GT40 kit. What we are talking about here is approaching a million dollars.......................
Anyway, I digress.................go for it.