I've heard of 'em.. don't know if they were factory equipment, i've never seen an 'original' one, but usually by the time I get my eyes on an old truck, the original bed wood is long gone.
I don't guess it would hurt anything to have one on there, but on the same token, I don't think the radiated heat coming off the exhaust pipe poses that much of a threat to the bed wood, either.
