Here is a view of a GMC set showing the hardware and instructions referenced above. I have a NOS Chevrolet set and it is a very high quality, well made part. I have not seen a reproduction set so unsure as to how well built they may be?
https://www.flickr.com/photos/advance-design_parts_co/29379381668/in/album-72157631868452754/A secondary note these parts are accessories not options which carry an RPO number (Regular Production Option). These parts were available at the dealer parts counter, they could be installed by the owner or service department. As such these would be appropriate for your 1950 truck. This accessory appears in the Salesman Data Book for 1950 on page 218, in the 1950 price guide (attached to the book) they are listed at $7.50 per pair both 1949 & ‘50.
