That hole was there as part of a grain unloading chute. You can see the chute
HERE. I have no idea if the chute was an original part of the bed, which is a grain body made by the Perfection Steel Body Company from Galion, Ohio, or an old farmer add-on.
I ended up removing the chute and filling the hole with a piece of native white oak from my old barn. It was nearly a perfect match for the original boards on the bed.
There is also a 6-inch square hole approx 2 feet in front of the axle, just to the passenger side of the drive shaft with a sliding steel plate underneath it. I was told it was for dropping grain into a portable auger pit or tub where it would be elevated into a storage bin. I kept that operational, you know, just in case I wanted to haul a couple hundred bushel to the local elevator.
