Most of the trucks were outfitted by the dealer with various flatbed/dumping/hauling set-ups to meet all the different needs of commerce through out the USA. The flatbed boards that left the GM factory were not tongue and groove. They used metal strips that sat recessed in grooves of the wood. The metal strips were higher than the wood deck thus ease of sliding items around. There a many pictures of this set-up on this web site and the sites that sell trucks. Of course GM did sell trucks with a stock boards and paint jobs. If you search vintage chevy truck ads in Ebay you will see them.