Rear air blows hot air!!!!!

It sounds like you have a stuck or damaged blend air door for the rear. It determines if you get AC or heat.

A/C on max A/C and fan speed on low i get a reading of 51 degrees. My pressures by my gauges are 45 lbs on low side and 235 on high side. Rear A/C has been removed years ago, A/C has worked well since. Driving at night my A/C temperature gets as low as 42 degrees. I am thinking condenser.

pressures does not seem to be that bad, but you never put the temperature outside in so we need to know that when you put in pressures. it may be the blend door not fully closing or if you have a heater valve that may not be closing either. at night it is cooler so will A/C will cool better anyhow.

Sorry, outside temperature was around 79 degrees. Just drove it around twenty miles, the further i drive the colder it gets. Reaching my destination with a temperature of 48 degrees, but temperature immediately warms as soon as vehicle comes to stop. It went from 48 degrees to 58 degrees in less that two minutes.

check to see if your cooling fan is working it may not be as to why it gets warmer when you stop. if not check fuse and relay under hood fuse box at least one should work when a/c is on. then check for obstructions in front of rad/condenser. if you have one of those "bug screens" take it off and throw it as it blocks about 15% of air flow

Single fan..belt driven....washed condenser fins with garden hose...no obstructions...

Has fan clutch is operating as well.

as long as this is not auto temperature control where you set the temperature then it is either a little low on Freon, maybe low vacuum getting to blend door not letting it close all the way or what I have said previously.

No, all manual controls. Going to A/C shop to get checked out. I will update after repair.

even manual control has vacuum for blend door. so it just may below vacuum and when you get to a steady or close to it speed you get better vacuum so it closes blend door more. Or the blend door may be broken too.