Not wanting to sound rude but for all the effort the choice of an L series would be a waste of time and money, as has been said already you can get as much power out of an A series anyway,
You could build a sleeper 1700cc stroker and there are no structural changes required and it still looks like a 1200 to nosy buggers. If your intent on going bigger look at the later
technology from Nissan like a CA 1600/1800 or the alloy SR series. Or if your really keen an alloy quad cam Nissan V8 ! I've seen one in a 310 Sunny and theres plenty of room. But any
engine swap will require the gearbox tunnel to be modified (wider and probably higher) unless you can find a car that was an automatic as these usually have a bigger tunnel.