I bought a dust cover on ebay for my 1873 in 32WCF, and the auction said to check out his other 1873 parts, so I did.
Looks like he took a complete rifle, and simply parted it out; everything but the receiver was up for sale. That seems like a shame to do, but out of curiosity, I followed all his auctions to see what they closed for. He sold for about $1200, when the complete rifle was worth something like $800. So there is a market out there for parts.
Even rusty, I bet you can photograph and document the amount of rust, and people will still buy it. If I am missing a pert, a rusty replacement is better than no replacement ... could be a fun project.
By the way, my dust cover is a little looser than I would like, so if you decide to part this one out, I might be interested in the dust cover .....