Minimum required-at least one arm. At one time Marbles listed a tang sight that worked with the tang safety. Look for it to be $100-125. After that, the tab goes up. Whether you get the Lyman 38 reproduction from Buffalo Arms or the bolt peep from Frontier Americana, you're looking at $225 plus installation. Even a Lyman or Williams receiver sight ($50-85) adaptation will have to include $ for having the receiver drilled and tapped. Ditto for an XS. BOL