I have a 1950 GMC which my father bought new from his brother who sold GMCs My father immediately installed a metal plate over the entire bed because he delivered fuel oil in barrels in those days, and wood would not stand up to barrels being handled on them. The original wood is still under the plate. I recently lifted a corner of the metal plate and there is no sign of ever having any paint. We also used heavier flatbed trailers with yellow pine floors. When we installed a new floor we moped it with linseed oil on a hot day. We would sometime pour a little paint in the linseed oil to give it a little color. I clearly remember new pickups smelling like linseed oil. My guess would be that GM put a little black paint in linseed oil and moped it on as a preservative and giving it a flat black color. GM may have done it, or it would be my guess they bought them already treated. It was definitely not creosote. I used to haul creosote posts to the electric coop here before it was discovered creosote causes cancer. Creosote has a distinct odor, and new pickups did not stink like creosote, but they did stink like linseed oil.
