You've got a D15b2. Any D-series engine would drop in fairly easy. you'll need to mod the wiring harness, but the easiest with most gain would be the D16z6, SOHC V-tec from a 5th gen SI/EX @ 125hp. You could use the stock tranny/axles with that setup for simplicity and cost. No stock civic uses a B18, that's the integra engine, and yes a different tranny/axles would be required. Good luck,

Jung