Lawrence your a gem Not sure about the Phillips screws but you know that . Isn't there a dump or a derilect building or boat to find old dome header s?. If I could comment I would suggest you cut away the long fore end the rod usually go's up the near the lock so less rod channel & short hole to drill one iron pipe is usualy thought enough .Not shorten the stock any , just let more rod channel be visible Heelerau has a lock of my make perhaps he might send you a pick inside & out , they are quite basic ' rough as bags' actually but that's the style . as to sights they seem to have an iron pin fore & many had a tapering tube rear appeture in effect about the size of a 303 case sans neck & base . for Big piggyjacks might consider a plug B' net kind of goes with them anyway . I once engraved on the under side of a M lock ."Built a better matchlock & the World will beat a path to your door "! Hasn't worked mind but seemed fitting . Another one Had "Matchlock shooters of the World ignite ! 'You have nothing to loose but your brains !" ( He was a Union rep ) & my pet snap matchlock had "genuine selected 5 $ Montana barrel reject'' & it was .
Regards Rudyard