Brit guns I have re tapped to 5BA.
Screw choice is easier then.
Bit of file work on the head & re engrave.
Screw head engraving is usually simple straight line stuff.

Sometimes I buy a cut up, de registered parts gun from a dealer.

If the gun is too badly gone it gets the hinge pin knuckle cut off with a 14" metal cut off saw, struck off the register as a destroyed action & sold as parts.
O.M