I have both Mossberg's 835's and 590's. And I can tell you from FIRST HAND EXPIERENCE that everything from the front of the receiver of the 590 can be moved to the 835, as long as you don't mind loosing the 3.5" capability.
But you can also order an 18.5" Heavy Walled Security Barrel direct from Mossberg for around $100-$120, the difference between Matte Blue and Parkerized. Then add the 4.25" Choate +1 Extension, and you basically end up with an M835A1
that will handle everything from 2 3/4" to 3.5" 12Ga. shells. Mine will also feed and eject without any issues the Aquila 2.5" Mini-Shells.
If you want the Mossberg Part Number for the 18.5" Heavy Walled Security Barrel, let me know, I'll give it to you.