Before you act, get the serial number to holland and holland and confirm the original configuration for choke and barrel length. You should not alter it without knowing for sure. This is especially true if resale value is important.
If it is altered you could have a barrel jug choked. I have a 16 ga Purdey with cut barrels, confirmed by the maker, which I have put briley tubes into and through some stock work and a lighter recoil pad moved the balance back to its original point. It is a sweet gun, but resale already ruined before I brought it.
I advise caution if resale is important, if shooting it yourself is critical then after having the wall thickness at the muzzle measured to ensure they are thick enough for jug choking, then i think that is best for less impact on resale while making it more useful to you.
I personally would put briley tubes in it, if the barrels were cut, but many find that an abomination.
One last word before you alter chokes of you reload there are things you can do to tighten up patterns some such as harder shot and taping shot wads, test that to with both targets then a patterning board. You may find your need for tighter chokes in the barrels is not as great as you think.
