Welcome to NICO!
I wonder if something from these guys would work:
http://www.pertronix.com/prod/
I have a chevy small block in my boat, and I used one of these and it's great not to ever have to adjust points or anything like that. I have also done it on a big block Chrysler and it worked great as well. Probably the best bang for the buck to eliminate that points and condenser.
Worked fine with the stock coil and distributor cap and whatnot. Not sure what kind of distributor those older nissans have, but I bet you could find something that works, after all they all work on the same principle.