67 C10 new bed floor not lining up mside to side

[LS short box]

My short box parts were all aftermarket except for a mint stock tail gate I found locally. The wood for the bed came from a vendor on this web site but I believe he doesn't sell the wood any longer.
Have you squared up the box itself corner to corner?
I had slot a few holes a bit but all in all the sheet metal was good.
Got any pics of you box with the wood installed?
Pic of my box.