First, the bed I have does have a PN on it (in stencil) but I it does not cross reference to the SNL-G-508.
The bed is marked 'Drawing No. 7064280'
This is most likely a post war supply stencil:
Here's the sill:
Note the ends are tapered.. t must have been installed on another truck
I have no doubt that it's an original CCKW bed. If its not an original sill, then someone took great pains to add in the tool box and frame mounts on the rear:
Here are some more pics:
One thing to note.. it was mentioned that there should be reliefs in the wood for the frame rivets to go into so it lays flat. THIS IS WRONG. I have proof! you knew I did.
The rivets are just above the center of the rear bogy. Look at theis ORIGINAL wood bed still bolted onto the frame. NOTE THE CUTOUT FOR THE RIVETS.
All in all, I do no not thing the depth of my sill is correct. Length and width are.
2 1/8th wide
4 3/4th high
11 5/8th long
But I think the BIGEST suprise is that cutout for the rivets.