Just use it as-is. You've got 2 3/4" chambers.
Opening forcing cones would have had to be done on every shotgun made before the 60's if the then new plastic wad ammo didn't perform in them or was dangerous.
I'd take it easy on the loads only because that's what I do with any older gun. I have no doubt the shotgun can handle most over the counter commercial loads but why subject the gun, stock and you to the punishment.
Plenty of 1200fps loads and reload recipes around that keep the pressures down.
If the Fuller Bros chokes aren't to your liking, take those out perhaps.
Personally I like them that way. Nice for skeet.
Nice looking shotgun. Some good buys still yet around in German & Austrian SxS's
