Not sure how much data you can get off the stock narrowband O2s - just a lean or rich reading.
You'll need a wideband to get a true reading (from one of the analog 0-5V outputs)
To hook up a gauge designed to work with a narrowband O2, I believe these are the wire colors you can tap at the EEC... double check the wire colors on the O2 harness.
No offense man but that thing might as well go in the trash. Its going to be the most obnoxious gauge you've had in your life with the light show it puts one and its damn near worthless for accurate tuning.
i'm pretty sure the OP got this installed 4 years ago at this point.
Red79mustang, this is a 94-95 mustang specific forum, you'd have better luck checking in the fox 5.0 forums for an answer. best thing in the world is the search button.