A/c manifold gauge hookup questions

I know its late in the season but i want to fix my a/c on my 1973 duster. I have done alot of a/c repairs on r134 systems and never any on r12. I ordered a new manifold gauge that has r12 hook ups. I rember when i was getting a/c training in college on old r12 systems one has to be careful hooking up gauges because both low side and high side has the same size fitting.

So havnt gotten an a/c diagram out to compare to see which is which but i figure here best place to get a fast answer.

i know theres a fitting on the passenger side of the compressor pump and one on the a/c line out of the pump on the driver side. Which is which?