engine swap question
 

i just purchased a complete turbo 2 motor minus the wiring harness.
im putting it in my n/a 1987 rx7. the one problem im having is that the online shop i bought the motor from didnt know what year the motor is.
once i get the motor how can i atleast know if its an s4 or s5? is it marked on the motor or is there another way to know? if i need to buy the wiring harness my guess is that i atleast need to match that up. or will any wiring harness work regardless of year. thanks for the info.