After reading all the posts today I think I have a plan. I'm going to take a couple sheets of 1/2 inch plywood and cover the entire bed, including around the wheel wells with a seam down the middle of the bed short ways. Then take some of the pink insulation stuff, probably 1/2 or 1 inch, and put it over the plywood cut out the same way but with the seam going the opposite direction. Might even put a couple slats down under the plywood between the ribs just to even the pressure across the bed. I'll have to see what the local HD has. Not sure, but I'm thinking about gluing the whole setup together. I think it might make it easier to handle in the long run, but I'll wait until I have everything assembled to decide that.
Last part of the fix is to get the crack welded and then have the bed sprayed with Rhino Lining. That I believe will help with any sliding around it does offroad. Putting in permanent guides is not an option as I use the truck for a lot more than just hauling the camper. Although I do like the idea. Might look to see what I can put together from some scrap wood blocks I have.
I know the crack came from the forest service road and the potholes along the way. It takes a good bit of time to get to camp without the camper. With the camper it took me almost 1.5 hours, maybe a bit more. Not sure how far it is. I keep forgetting to check the odometer. If I take it up next year I can guarantee it will take me even longer to get there.
Thanks for all the input.