A better hitch receiver would be my choice. The TITAN #45299. See etrailer. A full crossmember replacement.
And then diagonal bracing from the receiver tube that clears the spare to well forward on the frame rails.
Or move spare to bed and extend receiver tube to near axle. Several reinforcements as well as cross bars.
I'm going to use above receiver and cut up the cheap CURT Class V I have now to serve as forward portion.
Controlling flex differences on frame rail ends is goal.
A schematic from the 1960s will show how we once did it with custom receivers. Use those as template. I've posted link here before from 1968
Plymouth full size.
Andrew_T knows this stuff backwards and forwards.