Try replacing your condensor(capacitor) (the small cylinder in or attached to your distributor) no need to replace the points at the same time at this point.

I have had lots of issues with condensors, they seem to 'dry out' over time and new ones are made in china in small factories that are not good quality, i went through 4 of them within 2000 miles before eventually installing a points replacement kit. The tech wiki says this is the best mod you can do to your Datsun, and i have to agree...