schooling..
Wideband sensors generally do not make good replacements for narrowband o2 sensors because their switching speed from stoic to lean or stoic to rich. This can impact fuel economy as the EEC-IV teaches itself by gradually enriching the fuel until the O2 says too rich, then gradually leaning the fuel until the O2 sensor says too lean. if the sensor takes longer to say too rich or too lean, the longer the engine computer takes to correct things.
So for a daily driver it is better to keep narrow bands in command for the engine computer, and just add a wide band.
That said, if your wide band has an output to simulate a narrow band sensor, then you can splice that into the signal line that normally comes from the narrow band oxygen sensor. for folks using something like the LC1 which puts the sensor electronics closer to the actual sensor, splicing into the O2 sensor harness at the exhaust manifold makes more sense. If your electronics are in the car and the wire comes from there, then it may make more sense to splice in at the EEC-IV plug.