Porsche 917-10, 917-30
A Monument to Effort (Wisdom & Tragedy)
From Chapter 25 of the original edition of The Unfair Advantage:

"We baselined the old 917–10, ran the Carrera some, and proved out everything on the 917–30 test car—everything but the new body. With the car the same except for the new body, it wasn"t any faster. On top of that, it seemed to have a high–speed oversteer, no matter how high we turned the rear wing up. It was a funny–looking wing shape. It was almost flat on top and very round on the bottom. It looked a lot like the Porsche setup we tried unsuccessfully in our first development car, but since they had paid a great deal for the design, we felt obligated to give it another chance. We had no way of knowing the relative value of the new front versus the new rear, so we put the old tail back on, and discovered that combination was best of all. At least the new nose configuration was better. Still, the top speed was limited at 212 mph."