Would it Work? Probly. Would it be safe? Maybe, Maybe not. I woildn't trust it.
I've put Gosseneck hitches in a half dozen pickups by bolting 2 pieces of 1/2" 3x3 angle 8" long to the outside of both frame rails then Slid in and bolted a piece of 3/4"x8" plate on top of them, all the way under the bed. Located a hole slightly larger than the shaft of the ball in the center fo the plate. Weld the nut to the bottom of the plate. Cut a hole in the bed just larger than the ball. All it takes is a pipe wrench to put the ball in/out and material is cheap enough. Hauled some hellatious heavy loads thousands of miles with nary a problem.