Had a chance to work with the Rapid Prototyping Laboratory folks that work within the Prototype Itegration Facility (DoD Army) at Redstone Arsenal about 5 yrs ago. They utilize prototyping machines that are simply ridiculous, plus they have a whole building full of C&C machines and manufacturing equipment and staff to back it up.
I didn't have the GT then, but all I could think about was how sweet it would be to be allowed access to that type of equipment to produce car stuff. If you can dream it and draw it, they can make it in a week regardless of the complexity, electronics and big stuff too. Of course, you would need the financial backing of a country (say, the US) to be able to afford it.
http://www.redstone.army.mil/amrdec/pif/index.html