Why do you think the JDM ecu will be useless? I think you're confusing it with the RHD wiring harness on the B18C. The shock tower and battery connectors on the JDM wiring harness are reversed. You can either use your Civic's wiring harness and probably have to lengthen a few wires or get a USDM OBD1 B18C1 wiring harness. You'll also have to wire in VTEC, knock sensor, and butterflies.

edit: Sorry, I just read your post again and it looks like you knew this already. Yeah, getting another wiring harness is the easiest route (that's what I did). You can just unhook each connection on the old one while hooking up the new one. That way, you won't have any problems with where each plug goes. I still haven't gotten the butterflies to work yet (lazy), and I've read that some OBD1 B18C's need a ground for the butterflies, while others need a 12V signal or something like that.

http://www.hondaswap.com/forums/inde...howtopic=41608 This is pretty helpful as well, although I found that not all of the information applied for me.