Ed-
You can hold the cam in proper timing position with a pushrod in the roll pin hole, inserted through the pushrod passage in the cam cover. Do this with the piston at TDC, and you'll have the timing right. The timing marks are impossible to see when installing the cover, and trying to drop the cam assembly in place and mesh the cam gear with the crank gear is frustrating and likely futile. Harry Higley's 4-stroke book has an assembly procedure that will have you learning new obscenities and pulling your hair out. I can't imagine factory assembly being done any other way than by using the hole in the camshaft and an alignment pin (i.e., a pushrod) to hold the camshaft in position while installing the cam and cover.
Abel