Old roll-pin can usually be re-used as long as it goes back in tightly. Make sure the new drilled hole is exactly same size as A-series hole.

It seems to me Datsun didn't drill them exactly on center. But it is important to get them the right spot along the shaft so there is not excessive space between the gear and housing. They are two sizes washer for spacing.

I was just wondering how people have gone about drilling the hole through the E15 distributor shaft to install the a12 drive gear. Fairly important to drill directly through centre of shaft i'm assuming. Best done by a machine shop? Perhaps you just use a decent drill press and holding jig/clamp?

Also, do you have to provide a new roll pin or can you use the old one?

Cheers.