You've built a good looking model, even though it didn't quite match your expectations far as finish.
I've spent rather a lot of effort experimenting with various materials to achieve believable "bare metal" finishes. One of my recent ones is here...http://www.modelcarsmag.com/forums/?showtopic=81398
It represents a just-finished alloy body, and pretty well matches the 1959 press photos.
The body in your reference pic seems to have been stripped and then treated with a phosphoric-acid wash. That's probably why it's gray, and many of us were expecting "silver", as clean "bare metal" would be.