I got my issue with Pertronix figured out. Evidently, some Datsuns came with distributors that have a slightly larger diameter shaft between where the rotor sits and the cam for the points is......this is why teh magnet sleeve would not fit.

Pertronix is sending me a replacement magnet and I will bring my shaft in to have the protrusion lathed down enough to make it all work.

According to the guy I talked to at Pertronix, they developed the Datsun kit before they found out about these other, larger shafts and by then it was too late to redesign things.