Hey jumpa, found this article on Sheldon's site about servicing English 3-speeds, hope it helps: Servicing English Three Speeds
It's easy enough to fit an engine up top, like this:
then with a rag-joint sprocket you wouldn't have to "hack" anything up if a collector want's to buy it off you down the road.
Great find btw, should wait a couple weeks in case someone does come forward. You may end up rebuilding the rest of the owners collection for him, heh heh.