Over at The Dirt Forum, I was able to learn a little more about the truck.
While I was tinkering this afternoon, I was looking for the block casting numbers. I did not get that far, but I found the Intake Manifold casting numbers. 3927183 is listed as a 1969 2BBL Rochester Cast Iron Manifold that was used on either a 307 engine or a 327. I am not any closer to learning the displacement of this engine. But now I wonder why this is not the 1968 2BBL Rochester, stamped 3919801.
Could it be this truck was made late in the production year?
I also found out that the truck did indeed have an original wooden bed. Some of it is still there, hiding under a replacement steel floor that was put in no telling when.