I only need one plate and LEGAL in CA, ONLY if you have a 45 or 46 and running a DMV cleared 'Year of Manufacture' plate. In CA this is the one loophole allowing a single plate on a car or truck, I keep the DMV book in the glove box as most PD and CHP's are not aware of this. But, I have never been stopped.

And Im sure Chevy supplied both brackets.

It's easier to get forgiveness than permission!
1946 1/2-Ton Chevy
1953 Chevy 3/4-ton Factory Stakebed