Thanks. Now that I have the
oil pan removed I'll be able to check that the bottom of that shaft will mate with the
oil pump no matter what I do from above. I'll repeatedly install/remove the distributor to verify that that the drive shaft can be seated properly. I'll repeatedly install/remove the
oil pump priming tool to verify that that the drive shaft can be seated properly. After a successful "set of experiments", I'll be ready to transfer that oil pump to the new engine with confidence.
Just query on "Ford 460 oil pump drive shaft". The horror stories you'll find are mind boggling.