alright
sorry for being "rude"
OBD refers to emissions and electronics...
OBD0 is up to 91 civic hatch...
OBD1 is your 92-95 civics...
i'm pretty sure OBD2 started in the 96-00 civics...
now if you;re doing a swap you want to either stay in your OBD range, or go to a previous...
with enough money you can make anything work... but the idea is that you have plugs inside your car for your ECU, OBD plugs match likewise OBD plugs...
so if you want to do a sohc vtec swap in a 91 civic hatch, you need to either run an OBD0 vtec ecu, or get a P28...
92-95 sohc vtec is OBD1, P28 is OBD1, but your chassis has plugs for OBD0, so you need a OBD1->OBD0 conversion harness...
or a vafc but that a whole diffrent story...
look in the refrence section on this site for some great articles on this...
and a bit of advice...
sell the D16A1, 500 if you find someone who needs a stock replacement and get lucky, or 200, even 100, whatever
then buy a ZC from a good dealer for 400 or 500...