Thanks 440sixpack! It's all covered in the link I posted.
1. Mechanical gauges don't care.
2. ALL lights need to be changed.
3. Starter will work, just don't expect it to last another 50 years.
4. Generator/Alternator and regulator will have to be changed.
5. If the wiring is in good shape (?) it will handle 12 volts easily. Most 50 year old wiring isn't. You can go with a new stock harness and modify as needed or go aftermarket.
6. The electrical gauges and accessories will need to be replaced or have resistors installed. It isn't one simple resistor fits all, since the loads will be different.
7. Heater fans and any other electric motor will have to be replaced.
8. Ignition will have to be set up properly. At least the coil, maybe other stuff. BTW, one of the reasons they moved from + ground to - ground is the coil. Works better that way, as anyone who has got the leads backwards can tell you.