Keith,
Not sure what #8412 would be. Some models drove the oil pump off the inlet cam and those had extended hubs with a drive slot; but the EW switched early on to driving the oil pump via a worm on the end of the crankshaft. The cam wheels float freely on the cam spindle, trapped axially between the tappets of the front and rear cylinders. There shouldn't be anything touching or abutting either end of the cam, like a distance piece.
-Doug