You directed that question to Steve, but I don't think he'll be able to answer the question since it's not his truck, and I don't see where the info is listed in 68murc's gallery (the owner of the truck). So I sent a PM to the owner and asked him to check out this thread and hopefully he will respond to your question.
Sorry fellas, I forgot to check in. Thanks for all the kind words, it was nice to see my girl get recognized as the beauty that she is.
The bed floor is made of 1" Pine planks screwed to a sheet of 3/4" plywood. It's HEAVY!!! The screws are counter sunk and the holes filled with wood filler. I think it's just Urethane on the Pine. Dad made the floor for me back in '98. It still looks great. If I remember correctly it cost less than $100 to make at the time.