The truck: 2013 RAM 2500 shortbed Cummins. Bought the truck in May, realizing that fifth wheel hitches were hard to come by. So, I designed my own and had a local welding shop fabricate a set of custom mounts. I now have several thousand miles of towing a 7500 lb. fifth wheel on it, and have had no problems whatsoever.
The mounts were made of 1/2" A36 steel plate, then powder coated. If anyone wants 'em, I made dimensioned drawings of all the bits & pieces that I can email to you.
Here's one of the mounts: https://picasaweb.google.com/lh/phot...eat=directlink
One feature that these have over standard universal mounts is that all four bolts in each bed rail attach to a frame mount, rather than two in the mount and two just through the bed.