Classic/Antique Car Repair: Depressurizing A/C on 1968 Firebird 400, refrigerant, thanks in advance

Question
Hello, I just recently started to restore my 1968 Firebird 400.  I am working to pull the engine and I need to remove the A/C compressor but am stuck on how to depressurize the system.  It's currently still using R12.  Any help on how to do this is appreciated.  Thanks in advance.

Answer
It is illegal to dump R 12 into the atmosphere. The refrigerant must according to law be removed from the air conditioning unit by an approved recovery machine by a licensed operator. That is the law and I cannot advise anything that will break the law due to liability. When I pulled the engine on my 79 Pontiac I simple laid the A/C compressor to one side still connected to the system.
Brad