Does the end of the pump that goes onto the end of the timing gear/camshaft have a beveled edge? I seem to remember that, but it's been a long time. If so, I think the bevel should face the cam to assist in alignment and slipping into place.
Other than that, I would expect putting the eccentric at max or min stroke would allow for easier line-up. It would then be 'in-line' with the centerline of the gear, and only need the 'length' of the stroke adjusted for it to fall into place. Don't quite know if that describes it effectively...
tom