Air/ fuel tuning

Air temperatures will change the air density slightly, not enough to worry about, esp 20* F.
Engine temperatures make a big difference to the combustion and will effect the left over oxygen even if the AFR in doesn't change.

Exactly as Aaron posted, set the idle for best power in gear. If it noticbly drops rpm when going into drive, that's an indicator. Vacuum is a good indicator too. If there's a lot of exhaust dilution due to a radical cam, it will want toward the richer 12.5 and with more mild toward the 13.2 AFR.
(For stateside late 60s early 70s requirements, the AFR at idle was to be 14.2 and initial timing around TDC. If you don't have to go there don't.)