What A/F Gauge do you run

Cheapest is a narrow-band O2 sensor with a rich/lean indicator. Holley and MSD made one that look similar, with a tiny box. Most have 3 LED's w/ the center one meaning "ideal". List price is ~$170 incl. sensor but I bought 2 off ebay for ~$25 ea, one was never installed. Any narrow-band sensor will work ($15), though they use a 3-wire type and Weatherpack connector (recall).

You can later upgrade to a wideband sensor kit since all use the same O2 bung thread. Indeed, I welded 2 bungs in my exhaust (single pipe) so I can run both sensors and use the narrow band one to calibrate the wideband. Almost as easy while you are doing the job.