Welcome to the 'Bolt.
I believe that it depended on which trim package the truck originally came with... if it was standard trim, the bumpers were painted.
If it was deluxe or another higher $ trim packege it was chrome.
That is, if the chrome shortage caused by the Korean war was over by that time...
I'm fairly certain that the trucks didn't come with stainelss steel bumpers.
If you notice the truck on the opening page of the 'bolt you'll see the chrome bumper and chrome grill.
Also poke around in the gallery section to see some other options.
At the end of the day it it what you want to do to your truck.
Some websites with great information in various articles that you can use:
http://www.chevytrucks.org http://50chevy.freeservers.com http://www.speedprint.com/Deves50/ -W