Cadmium plating was frequently used on hardened fasteners in industry as cadmium does not promote hydrogen embrittlement to the degree that zinc plating would..albeit both processes require a post plating embrittlement relief bake.
For us guys zinc plating is what works best IMHO and could have been the norm back in the day. Industry had both Cadmium and zinc plating shops.
Cadmium plating has been under the watchful eye by the EPA in the US and banned in the EU so getting something cad plated today could be costly.
70 years ago EPA and OSHA weren't on the radar as they are today.
So does it really matter?
Great question!
For me personally, it does not matter. I am not going to spend the money or risk the health of humanity by cad plating my parts. I just paint them with Rustoleum self-etching primer and follow up with Rustoleum Metallic Silver paint which matches what I found under the putty used between the hinge and the cowl.
This topic would matter to someone who is restoring his truck to as-built condition for judging by experts in the field.
