I do have the regular 51 plates, like the one above. I will use them on my 51 suburban.
I have not found commercial plates for my 53 truck yet.
I also need to find the 53 corner tabs.

A good sourse of info was sent to me by 41chevy (scroll up and click on the link)

Hopefully I will run into something at the Turlock swap meet (jan 27th-28th).

Good luck
Javier