high side and low side locations???

I don't think there is an exact standard for R-12 fitting sizes. On my 1984 & 85 M-B cars, I recall both high and low pressure ports were the same fitting when I converted them to R-134A ports. Confused me for a while.

If you plan to convert from R-12 to R-134A at this late date, you might want to read up since R-134A is already outlawed in several countries and planned for the U.S. too. However, alternates also use the same R-134A fittings (Duracool, Envirosafe).