Second option (one i will be doing in about 5 years) search for a caterham kit car. for about 3 grand you get a frame and stainless body panels. then you purchase a miata donor car and move over what you need to the kit. if you spend some more and get performance miata parts then you will have something similar to the real Caterham R500.
And yes i know all of this since I am actually entertaining the idea of doing this myself.
That's a lot more along the lines of the original Lotus 7 approach.
