If is really 1/2" thats a little skinny in my opinion. Milled dressed boards ( S4S ) run a heavy 5/8" to 3/4" depending on mill. If you are not planning to load the bed up you might be OK.
Sounds like you have a " bed kit " from someone.


1940 Chevy KC 1/2-Ton
In the Stovebolt Gallery