The best comparison between the two is in intent. In '53 and now, GM wanted to create an upgraded image for their brand. In the early fifties Chevrolet, while popular, always had a performance gap with Ford. Chevy was not associated with performance. They also wanted to show that GM, being the most successful automaker in the world, could compete with anyone anywhere. At the time there was a rising interest in sportscars by returning GIs and thier options where mostly foreign made. GM said "we can do that!".
Today GM wants to get back in the car business and improve the performance image of their Pontiac brand. They have promised us excitement, but by and large have not delivered. Again keeping and eye on the growing interest in sportscars, and the demand that has been met largely by foreign makes, GM has said, "we can do that!".
Both cars are a response to consumer dissatisfaction with the offerings of the day. In the fifties cars were getting bigger, heavier and softer. In the '00s we have SUVs and Pickups that are bigger, heavier and softer. Not everybody wants that.
The design and layout of the two cars directly reflects GM's desire to compete head to head with who they preceived to be the leaders in the market. In the fifties it was against cars like Jaguar, MG, Austin Healey, Kaiser and Nash. Today it is Mazda, BMW, Honda and Toyota and these cars are retro inspired by the sportscars of the past. Not to mention that I'm sure the GM design studio looked back at what had been done there before and said to themselves, "Damb! That was cool!" This is even more obvious in the Chevy Nomad concept. (which I also really like!).
Anyhow, I was not born soon enough to buy a C1 but I do have a chance to make up for that now!
