wu tang

i have a 91 hatchback its the standard model. it's a 4 speed manual. and i am putting a si motor in. i dont know what year the motor is. but i know i have to add in some more wire's to my wiring harness. but the only wires i know to *** right know are the other 2 fuel injectors. heres my idea..go take a 90 to 91 si wiring harness and take out my old wiring harness and put in the si one. and will this work pretty good?? or what other wires will i need to include?? thanks for your time