the earlier A12s (from 1200s up to 73 i think) had the dizzy at the front of the engine and the alternator on the passenger side.
later A12s (which are more common) from 120ys and sunnys had the dizzy back further, and the alternator mounted on the drivers side, this made room for a aircon pump where the old engines has there alternator

as for performance, i dont think it really changed in that aspect, but some one with more experience will be able to answer that