Here is something to check. I recently installed a new Vintage Air, generation 4 air conditioner in my 47 Chevy. It was blowing at 38 degrees, but I was not real happy with the volume of air it was blowing out. I checked the voltage at the blower with it running, and found that it was over two volts lower than the battery voltage. I ran a separate 12 gauge power wire from my battery cable into the car just to power the air conditioner, and used a relay triggered off the ignition switch to control it. Problem solved. It made a large improvement in the volume of cold air.

Also the quality of your fan at the condenser makes a big difference, especially when you are stuck at a stoplight. Adding a bigger fan, or building a shroud, or adding an extra pusher fan in front can really help.