First question, is it cooling correctly?
If so don't mess with it, just putting a set of guages on it will cause a loss of charge, they only hold around 17 ounces of freon. They use R-22 so save your R-12 for something else. According to my Armstrong manual at 95 degrees outside ambient temp suction pressure should be 74 psi, air off of condenser should be 106 degrees and air off evaporator should be 61 degrees. This is a very good manual, if you would like a copy of it in it's entirety I could fax it to you, a lot of very detailed service instructions included. Just send me a pm if so.