80 sc a/c question
 

Hooked up the gauges, drew suction for a couple of hours, checked later and it held , put 2 cans of 134 in at 2000 rpm with a fan over rear condensor. High side got up to 250, low 55 at 92 degrees outside temp. Do I check final pressures with engine at 2000 rpm or idle? Thanks Any easy way to check temp at front vents?

Engine at 2000 rpm. Stick one of these thermometers in the A/C dash vent closest to the evaporator:
Robinair 50945 Pocket Dial Thermometer - 1-3/4" Dial Face, 0-225F