The guys at DDR Motorsport have put their brand-new Miami GT kits on the market. The kits all sell for right around $20 grand, and can be set up to accept the four pot from either an Acura RSX or Toyota MR2 in Sport Prototype 4 form, or the LS Series small block from the Chevrolet Corvette in Sport Prototype 8 form. The idea, DDR says, is to put a truly affordable supercar on the market.
For your $20k, you get a full tube chassis, an unpainted fiberglass shell, lights, signals and all the glass. What you don't get is an engine or any running gear. Though they can't supply the drive trains, DDR will happily explain how to get your McLaren F1 lookalike up and running.