The m/y '77>'80 schematics are all broken out by "loads". Each load has it's own schematic in the service manual so that they are much easier to read/use. Another good reason to own a service manual.
On top of that, there were two distinctly different a/c systems used on the '77>'80 sii if so-equipped on the assembly line and not a dealer-installed kit.
The schematics for both systems are attached, I wrote the application of each on the sheets before scanning.