Oil Pump Drive Shaft ?

You are on track. The carrier and the shaft are an assembly and will push from the bottom. Cam shaft must be removed first.

Please advise. Had to drill out shaft set screw but still not sure how shaft removes. I understand it removes from top but it looks like square drive collar at the crankcase end would prevent this. Is there a pin or something that holds that in place or am I way off track thanks.