I have done several. It takes to long. There must be shortcuts.
I do want a metal cutting bandsaw for cutting out the plate, it will save time for sure. Which one? I'd love to have a giant vertical machine but can not fit it in my shop.
My process is as follows. Grab a piece of mild steel thicker than the boss on the plate. Mill it to the thickness of the boss. Them mill the remainder to the thickness of the plate. Drill the frizzen pivot screw hole. Screw the plate to the old plate. Use a transfer punch to locate the sear spring hole. Secure the new plate to the old plate with two machine screws. Use transfer punches to locate the rest of the holes except the bridle hole. Drill and tap the holes as needed. Drill and ream the tumbler hole. Use the tumbler to locate the bridle screw. Assemble, check function, shape the plate to final dimensions.
Here is one I finished yesterday. The Siler plate was not right for this build. Excuse the trigger, it was my first build and I made the stock to long. There is no shortening it because the patch box is to complicated.