BRAYH33-1A01 Old Hupp freezer - Help charging freezer with R12

[Deserttoad]

Model Number

BRAYH33-1A01

The freon was drained out of this old Hupp freezer compressor and I need to charge it up. I only see this one port which I assume is on the low side? Obviously I will vacuum down the systems and add oil with the R12. I need to know which oil to use and how to know when the system is full. Can I use a gauge on this port to tell? If I weigh it in, how much R12 is correct since it's not on the data plate?

Thanks for any help