How does one unused museum piece bring about "more of them available"?

Such a claim requires substantiation in the form of multiple "for sale" offers of that model transmission.

http://stores.ebay.co.uk/Dronsfields-Independent-Mercedes

Mercedes-Benz Parts - Dronsfields, a Mercedes Breaker UK

Dronsfield's didn't have the transmissions on the ground in their shop. But they had a means to get them.

The salvage yard business is quite different than many other industries. You can't call Amazon up for something out of stock and say, I want "x" you don't show it, now find me 10 of "x" and call me back when you're ready to get paid. Salvage yards in the USA do exactly that, they all communicate with one another and will source for you what they don't have. Sure they take a small cut, but they will do the leg work.

Those guys seem like a good source if you all want to coordinate a group buy of unobtanium that is available in Europe. It's too hard and costly to gather a crate filled with maybe 100+ parts and ship them all DHL/UPS piece by piece. Go through 1 source, have them gather and prepare a bulk export shipment in a wooden crate, and pay 1 bill to 1 yard.

If I were ya'll I'd find a "group leader" or two and compile a list. Have just one leader be point of contact to the European supplier and see what you can do. If everyone all of a sudden bombards European wrecking yards with small order requests they will quickly just start saying no if they feel bothered. Single piece small orders are an eBay sort of thing. Overseas vendors will do some leg work if 1 person spearheads and effort to get an entire crate of goodies exported to the US.

Also the yards will mark up freight 50-100% if you ask them to handle that. If no one here is a freight broker who deals in ocean freight I can reference a contact that does small volume container work usually through Maersk.