Wooden bed or Steel bed?

[Chevtruckguy]

Hello everyone, hopefully this will be an easy one to answer.
I just bought a '72 Cheyenne and right now it has a wooden bed in it, but not sure if it was original to the truck,the truck looks like it had been restored or at least painted once before.
so is there a way that I could tell if the bed was on the truck from the factory or if it was supposed to have a steel bed ie. vin number etc.

Thanks
Erik