Will a JDM PR3 B16a ECU be compatible with the USDM (B16a head & B18a block) LS/Vtec I'm putting in my 89 Civ4door?

 

yes.

 

You'd probably be happier with 1.8l fuel maps.

I usually reccomend OBD1, it's easier to find parts.

You'd probably be looking at getting OBD1 distributor, OBD1 ecu, and either new injectors, or adding/removing a resistor box. Oh yeah, and an ecu conversion harness.

But you have options, and yes drift knows what he's talking about, and it will work.

-PHiZ