Right now I have a 1993 Honda Civic SI with the original z6 VTEC harness onto a OBD2 B18B motor. Bought the car like this so I could soon change it but harness looks like a jungle and when I bought the car owner was saying it had a bad throttle body. Car will shut off whenever it wants when I'm driving and half the time won't then back on until it wants to. I plan on getting a B16 head and getting my motor ready with the right gaskets etc, but not sure which model head to get, obd1/2 and which harness is the easiest. Don't want to spend all kinds of money on seeing what'sup with the b18b head because eventually I was going to get the b16 head.

 

the obd of the head makes zero difference as obd is the electrical system that runs the engine. get a good condition head...
and i have always modified a stock harness that fits the car since its easier to extend or add wires than completely repin the big plugs on the end of the harness.

 

get newer production head. less chances of being busted or worn to shreds..
and get obd2 harness because its now easier to find NON busted parts for obd2 simply because of how old the b series parts are.
injectors are gonna have less miles, all the electrical system would be less abused since you cant chip obd2 most people leave it stock or switch to obd1

I switched all my cars to obd2 ending harness and sensors. a lot less headaches since then and parts are easier to find

obd1 parts are limited to 93-95
obd2 parts are 96-01 so few more production years = more parts available

as far as harness,
gsr harness is easiest to find but you will have to extend the IAT sensor wire
b16a2 del sol harness is tough to find same with usdm type-r harness both of which will work without modifications
you can also use a d16y8 harness with few modifications that's very popular option since its cheap