Bed floor id help needed.

[Twisted67]

I am new here so first off let me say Hello! Here is the problem, I just bought a 67 GMC short bed wide side last week as a project. The bed is in good shape outside, but the floor is another story. It just has a piece of plywood bolted down to the cross sills. How can I tell if it was a metal floor or wood floor in its original condition? Also, if it was metal, where can I get a new floor? Is it possible to cut out a long bed floor and trim it to fit? Or is that a waste of time? Thanks for the help! Nate...