greetings all-- first post here. i'm contemplating the purchase of an m1 super 90 w/ a mag extension. two q's-- it has a 19.75'' bbl., but that didn't seem to be an option for this gun per this website. perhaps an older manufacture? second, it has rifle sights, but i would like to install a ghost ring. can an aftermarket gr assembly be purchased from benelli? it apeared to me from the website that only the tritium inserts were available. thank you for your input.