Why ask here when you can call Mossberg and get a safe answer? The answer might even be in the wbsite FAQ section.
I don't think they can be swapped. We raised 5 sons here on our farm and had a couple each 835s and 500s. I asked Mossberg once if the barrels could be swapped and they said "No" since the shanks were made differently to keep folks from doing dumb unsafe things.
Lance