For only $5250 USD you could own a 2915-3 caseback, and a collection of other bits that resemble a speedmaster! http://m.ebay.ca/itm/Omega-Speedmaster-Ref-2915-3-Chronograph-321-von-1959-RARE-/121821835753Purchases made through these links may earn this site a commission from the eBay Partner Network A very good price considering that 2998 caseback posted a week or two ago for almost double the price of this one.
There's also a 15,99x,xxx 321 movement out there (even though that may not be quite correct for a -3), starting bid €1800. Likely from a seamaster but, will we ever really know? It's a put-together just waiting to happen!