Modification question, would it be right

[Bernie Cross]

A question about what to do. An early 1900s classic English SxS 16ga in very nice overall condition. Not a London Best Gun. Barrels are 30" and do not appear to have been cut. Chambers are 2 1/2" and chokes measure a cyl/cyl. I cannot confirm original specs as to factory chokes, but I question the cyl/cyl.
As 16ga 2 1/2" shells are pure unobtainium and probably will be for the foreseeable future would you look to having a good smith lengthen the chambers to 2 3/4"? I currently load low pressure 16s in that length for a 1912 J.P. Sauer that had its chambers done at some point it its life. I do not like altering a gun but I hate to see a solid, well preserved gun become a display piece b/c ammo is not available. TIA