No one. They all have flat sides, a different crossmember three from the back, and some bracket differences. None are big deals, but short of galvanizing an original chassis, there will be differences that are obvious on a cursory inspection.
You can order a Richards with the NAS crossmember and set up for the metal tank at least that is what I have. It came from AB. It even has the reinforcing saddles by the fuel tank.
The one thing that upset me the most was the mount for the speed sensor was fully welded and not slotted. That slot will be a PITA to cut. I need to get to the garage to cut that slot and drill all the holes for the fuel and brake lines so I can get the body back on before winter. Should be a solid day's work.
*not legal advice*