I'm curious what outlet temp your getting.
My a/c used to be really cold with the R-12 freon but my compressor went out and I replaced it and switched over to 134 freon.

All I can get is 45 degrees with the thermostat all the way down and on recirculate in the rain at 75 outside air temp.
My other vehicle will get down in the 30's at 95 outside temp and it has 134 freon.
Thanks
Herb

I get 45 degrees out of my '82. I think it would do better if the fan had a faster speed or greater volume, because cold air RAPIDLY warms with distance travelled.

GM Says average evaporator discharge air temperature is approximately 33 deg F. Then it should get up to 35 deg F by the time it gets to the vents .
David