A good pump, maybe with a slug barrel and 28" choke tube barrel.
I prefer Mossberg (or Browning, don't have one) ergos, but any good pump that you like.
For ME, hunting Texas snow geese as I do, i'd make it a 3.5" chamber. It's a specialty load, but don't hurt to have it chambered for 3.5". Will still handle dove loads or whatever else. My new to me Mossberg 535 handles 3.5", my 500 doesn't. No, 3.5" aren't overrated if you have a use. Snows are an example, unless you wanna take out a second mortgage and buy some hevishot.
I shoot 10 on geese, though, patterns are amazing.
Amen! I could fill a dump truck with the ducks and geese I've killed with 2 3/4 and 3 in 12g. It seems that calling and proper deke sets have become a lost art in favor of long passing shots.
If you've never hunted Texas on a clear day, you have no clue what you're talking about. And, don't pull experience on me, I started hunting snows at 14. I turned 60 recently. I know all about rags/deeks, and calling. The problem is steel shot, not case length. Case length is an attempt to add BIG T shot in sufficient numbers. Ts carry a punch way out there. 10 gauge, though, patterns 'em better.