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...
thanks for the reply, I finally got it, I was trying to put it together with the pump on the cam and aligning the ball,finally glued it to the bottom case with some grease and it fell together. you're right , the pump does have a slight bevel