Mechatronics

I just got a call from my parts supplier that the ICM module in the 92 civic could be a Hitachi or other brand There is thee mounting holes or two mounting holes for the ICM module. Can some one cue me in to which is which? And can the distributors from both brands be intershwapped? I am starting my mobile mechanics business after being out of the trade so catching up on things again

Also, this Honda put out a code 15 or 16 but cannot recall which it was. At the time, I looked it up and said loss of rpm signal. The spark plugs had spark but changed the distributor with another one and it fired up. Was it partial failure of the ICM model, the hall effect pickup or what? I know the ecm on most vehicles usually require a rpm signal to put the injectors into run mode.

Thanks