I remember reading an article in a Britsh mag few years about a small
production car designer.
I can't remember the name,but  I was something like Caterham, Westfield,
TVR, etc.
All those smal models. They built a convertible, that used Ford Mondeo
(same as Contour) rear lights. it had a mirror like paint. really nice.
He mentionned that  when starting a new projetc, he was always starting
with the rear lights.
They had to used already approved parts.
He said it was really hard to properly finish the end of the car and
keep the overall line or design.
So he was always starting with the rear lights.

He mentionned going to a place, near the motorway where he could see
many many cars. He would pick a recent model and built it from there.