I can feel your frustration!
As i see it you are left with two options.
Restore them to functionality.
Professionally Restored.
If you take your time it would be fairly straight forward to restore them to functionality.
The back action gun will be the easiest, take a couple of measurements of the inlet and look around for some lock plates that are as near as possible in size to the original inlet or bigger with similar engraving, have the makers name engraved on them and inlet them into the stock.
If you take your time and carefully select your locks its amazing how close you can get them to fit, i recently completed a similar job re locking a back action gun, one lockplate fitted with only minor fitting and alteration of the inlet and the other was slightly worse and has a 1mm gap along the top edge - which i can fix by dovetailing in a fillet.
Then simply measure the new locks for hammers and order some replacement castings.
You could achieve a functional gun for the cost of a few hours inletting and perhaps 60 in parts. The quality of how you match the engraving, quality of inletting you do, and weather or not you get the makers names engraved will determine how much of a good job you can make of it.
You could do the same with the sidelock gun but i think you will have to probably make up new lock plates which if you do your self will be a boring and tedious job, and if you pay someone else, it will likely be expensive.
To have it professionally done you could have lockplates made up to as near as possible fit the original inlet but its going to cost quite a bit.
