Thanks for thinking of me, Shotgun Coach. Much appreciated.
I make a sight base that would work for the 586 to use Classic style sights. All I have are stainless steel ones for 686. If you don't mind the different color. This would require machining to mount it, though.
These would not work for a M13 because the fixed sight guns have a much lower front sight. A sight for the M13 would require machining as well, either a dovetail or a keyway cut and pin hole.
A barrel replacement of the desired length would not require machining.