The 59D distributor replaced the 45D distributor and can be used in any 1275cc A+ Powerunit.
Remanufactured stock distributors are good as new at half the price. As a distibutor wears out the control of ignition timing is increasingly difficult. While it is an easy project to replace the points and condensor, the distributor shaft and bushings that is worn will result in poor running, lower gas mileage and could even cause hard starting.
One of the best methods to determine the condition of your distributor is to simply use a timing strobe light and watch the timing mark on the flywheel at verious RPM's. It by the very nature of a mechanical system will show a 3 to 4 degree 'boucne' of the timing mark. As the distibutor wears out, this bounce could get to the point that it exceeds 10 to 15 degrees.