Narrowband goes to one or the other HEGO signal wires (check your EVTM to confirm which terminals in case they are different than the commonly-posted A9* terminals). You can use a switch to toggle between both banks.
WEGO is a Wide band Exhaust Gas Oxygen sensor. Wide band sensors are not used in the stock computer because they are not compatible with the computer's programming. The stock computer uses a narrow band sensor.
The A/F gauges that use the stock O2 sensor signal will jump all over the place. The reason is that the O2 sensors "switch" between .2 volt lean and .6 volt rich with a curve that looks like the drop off a high cliff. The curve is almost straight up and down, so the voltage shoots from .2 to .6 and back down . again 2 or more times a second at cruse. You won't get much useful information except when the mixture is extremely lean or extremely rich, there is no middle ground.
Use 43 (Dark Blue/Lt Geen wire) or pin 29 (Dark Green/Pink wire ) on the computer. Use Wire tap-ins from Radio shack P/N 64-3052. The computer is located under the passenger side kick panel. That keeps you from having to crawl under the car and make a weather proof splice in the wiring. You can use either one, or run a SPDT switch and use both. Then you can use the switch to select which side to view.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)