We just discussed this in another thread -
R12 System - Evacuate or not? It should help too.
System works leaps and bounds better with R12 than 134A. You probably need an entire system overhaul... condenser cleaning, evaporator cleaning, verify aux fan works, new fan clutch, be certain you are not losing airflow to the defrost pod, the recycle door pods work, etc.
You are in AZ like my pal in Mesa. Tint that thing ASAP with quality film, something ceramic and go as dark as legally possible. Use windshield reflective screens in the front AND back anytime you park, you want to keep as much of that sun and heat out of the interior as possible. Park with the rear glass pointing to the sun if possible, less heat on the dash, which is less heat for the evap to remove.
It will take four, 12oz cans to fully fill your car with R12. Buy it now and you can usually snag a can for about $25/ea. Wait much longer and you will pay the premium due to what I call 'the summer tax'. Since it blows hot now, I would just toss in 152A and get on with life as that can be done for about $12. Start cleaning critical components as you have time....do not be shocked to find out how nasty your evap is after all these years.
Been my experience that R12 will not leak from the hoses at nearly the same rate as 134/152A will due to molecular size. I am not talking about o-ring leaks.