In general I prefer to preserve the history of the gun.
Looking at the photo of the left side of the gun, neither of the two lock screws visible is original. What about the front one?
If the three lock screws are substitutes of unknown origin, I'd be inclined to make replacement screws that fit the lockplate holes - without using a tap.
As is, that is how the gun was used. But the screws could be replaced without alteration to any parts. That would restore the appearance without altering anything.
Does the lock work? Looks as if the mainspring might be missing.
Speaking of repairs and restoration, years ago I saw a respectable HBC gun which needed a new mainspring. Laddie found a replacement, installed it including drilling a hole, and welded up the original hole, thereby destroying the surface condition of the lockplate. Would have been bad enough if he had riveted in a plug.