why the swap ? is it cuz the motor went bad ? in that case you should use the same harness and same ecu just change the distributor.you should have all the old stuff like mass air,ecu ,distibutor from the old motor.in the end you win.s14 motors have higher commpression then s13's but they only red line at 6400 s13 red line at 7000 by swapping motors and keeping the old ecu and shit you will be able to take the s14 motor to 7000 giving you that extra power.just some advice think about it. :bigthumbu
also while your at it change the oil pan gasket. the gasket and gasket sealent are 10 bucks together.change the valve cover gasket too.also motor mounts to since it's all in the open.give your engine bay a good cleaning change all your fluids and change spark plugs and fuel filter .always when swapping motors give the motor a good tune up. if you can change the water pump and thermostat.do all this and you'll avoid lots of headaches and have your self i nice running ka.