fig would be easiest sr20 is pretty much all custom work. the sr20 from a 200sx will not bolt up to the front wheel drive gear box so you will need one from a pulsar. then to fit it into a micra its all custom work not worth it really cause you will have to spend on chassis mods and brakes suspension ect.
why a bigger engine? go turbo!! easiest engine to fit is a ga16 with not much custom work and most things plug and play. weight of the engine alone is maybe not worth it though
a guy from manchester rang me a few hours after and said somone was bidding on his account and he want to come and have a 'look' i said ok ring again when you want to come and hasn't rang since, plus his feedback seems very dodgy