i think youve got thing abit mixed up lol, if hes got an sR im assuming you mean SR20DET for a 200SX which had a 1.8 Turbo engine in it.
As an NSX is a honda and arnt 1.8 but just under 3 litters and are V6 lol a V6 Vtec powerd micra would be quick..
but as for fiting the 1.8T you can make anything fit into anything with the cash mate how much have you got to spend? io recone to have a company convert the micra to RWD and fit the engine would be reaching the £10K mark..