Anyone have a good recommendation for an 'economic' O2 monitoring setup?

[redz 1970 K5]

I really want a decent setup to monitor my exhaust and dial in my Carter AFB carb. I don't really want to go off of feel since that can get time consuming and rarely turns out right. I would like to know my O2 levels at cruise and on power to meter and jet my Carter properly.

I suspect I am lean on power and cruising, especially since the carb has never been dialed in after being tuned for 5k feet. I would even consider going one jet up or down if I knew what is in there now, but I don't.

OR, if someone happens to have tuned a Carter 650 AFB at sea level, I would LOVE to know your setup! That would give me the ballpark.