Dave, welcome to the site.
First thing, 98% is extremely good for a 1931 gun. Is this the seller's percentage or did you give it that?
The 26" barrels are not uncommon on a 16 ga., but I would make sure the gun came with them. If you post the serial number in post with the serial number in the Subject box, hopefully our records keeper will see it and respond on how long the barrels were when shipped.
The safety with a Hunter One Trigger will be manual and cannot be made automatic on a FW framed gun.
The slide selector could be a minor problem, but the stock has to come off to fix it.
The chambers would be 2 9/16" and were changed in the late 1930's. The bores still might be .650 as they were changed in the early 30's.
Post some close-up pictures.