The BMW-M1 was also a flat, angular design, but not nearly this flat.
Also, I think the BMW came along a few years later.
Anyway, I had gone back and edited my previous post to give credit to 'notfarnow'.
I must have been editing at the same time you were posting. sorry 'bout that.
Here is a good page with pics of the Lancia Stratos prototype, as well as several other flat cars. (guess I won't upload the stratos as a mystery car now!)
70's Supercars