wy dont you use a aluminium beerkeg sawn in half to cover the hump , those usually are cheaper make a lip on the bed in metal sheet and use these quarter turn dzus fasteners to keep it in place
as for the driveshaft either make a notch on the underside of the bed , raise the front part of the floor up to the notch or mount a driveshaft that has a second joint after the edge of the bed and make a crossmember with bearing to hold it in place
it looks good there sparky