Spreaders in a 16 are not hard to come by. RST makes very good ones. I wouldn't do screw in chokes because IMHO you have an older gun with this peconcieved modern contraption threaded into the barrel. I just really don't like them and have opened the chokes on a couple of Parkers but did it by going from full to Mod by reaming out the choke. I have never changed a choke tube even when I had guns with this option. I passed on a nice Purdy 16 once because someone put Briley thin wall chokes in it!
