I ran the ground to the ECU when I put mine in. I used this:
OBD1 Honda ECU pinouts - Honda Forum : Honda and Acura Car Forums
to find the right spots for my wires. I just picked one of the sensor grounds D21 or D22 iirc. For juice I put a voltmeter to test a couple of empty spots from the fuse panel. I found a good one and used it. There may be a good source in the ECU, but I ran out of patience testing different spots.