So what is the main difference between a 93-95 vtec obd1 and the 96 vtec obd2 motorwise? ECU difference? Intake manifold difference? What else?

 

The crank sensor moves to the crank instead of in the distributor. It adds the fluctuation sensor there as well. So it has a different oil pump that has the bolt holes for it.

The distributor is obviously different. Those are really the only differences other than the obd1-obd2a difference