Those pressures don't seem right according to the manual. Low side should be between 12-50 psi under normal conditions, high side 80-300 psi (rule of thumb is about 6-7 times the low side). 96 psi is way high regardless of close you are getting to a full charge, assuming your gauge setup is correct. There's lots of permutations of pressure readings and possible causes but here's a couple from the manual related to the low side reading too high:
Having low side above normal, but high side normal, it often points toward expansion valve problems. Is your expansion valve good and its sensing element installed right and clamped tight? If not, too much R12 flows, and your low and high pressures become closer together.
Having low side above normal, but high side below normal, it often points to compressor weakness/failure.
In the heat of Texas, it seemed like it was always 100 degrees and 98% humidity anytime you wanted to do A/C work or get paint to dry. On my 67, I always called mine "good" when the pressures were well within ranges, when the bubbles in the sight glass disappeared/reappeared quickly when the compressor kicked on/off, when only the right parts got darned cold, and when the system "cycled" properly without being annoying. That thing would spit snowflakes out the chrome vents when charged properly!
