Hi Lindsay,
I'm also restoring a 1915 2 3/4. I may have a crankshaft surplus to my requirements. It would be a later one without the key way for the flywheel, but that should not be an issue. I will try and get some photos of it on the weekend and PM you if you are interested? It won't be in fantastic condition but should hopefully be usable. I'm short of a few items so maybe we can do a swap?
Cheers
Ian