Beautiful install....
You could install a dual unit with fresh O2 sensors and do a careful free air calibration. I am bit biased for this unit since I have a single version of the this Wego IV instrument in my 1973 911 MFI and love it. Great instrument and great value for the money.
With this great motor of yours I would install a dual AFR permanently and have real time readings plus the bonus of 2 hours of data logging to look at on your laptop at any time.
Our host sells this one.....here is a photo:
