The two locks I bought were misrepresented by the eBay seller.
They were listed as a mis-matched pair (that part's correct), but we're supposed to be one LH, and one RH. Obviously I received two RH locks. One, on top in the first pic, would actually work and the trigger would make it fire if I trim the plate on the front end and add a cock/hammer. The lock and plate is a little smaller than the hole in the stock but I was prepared to make a new plate of all else worked out.
I haven't yet figured out how to use RH parts to build a LH lock, but welcome any suggestions. I need to trade a RH for a LH. I know my local Muzzleloader shop has some old locks so Monday when they're open again I'll go see if I can make a trade. Unless you're working on a SxS gun there should be more demand for RH locks I believe?