The A12 [rear dist] distributor should fit right in, but one from a 1200 engine [which is also an A12] would need to have the steel mounting plate at the base switched.

If your A15 is stock, then try to keep the stock distributor in it & switch the Pertronix parts over as the two distributors will have different advance curves & the one in your A15 is tailored to your stock engine
The one Pertronix part number fits about a zillion Datsun models, so if the original points are the same for the two distributors, then the Pertronix should fit.
[I love these things & my coupe has one fitted]

The fuel pump from the 1974 & up A12 [rear dist] should fit & work just fine, but the pump from an A10 & 1200 engine [front dist] will not.