It has been modified from stock. Do you know what refrigerant that is in the system? I do not believe R134a will be happy in a Suburban with an original small condenser core.
You are also missing the POA valve and using a cycling switch instead. While that setup was used with success in later trucks reports are it doesn't work that well in our trucks.
The belt is missing on the compressor, is it functional? Instead of a Sanden, I would opt for something like this
4 Seasons compressor. Sanden design but a direct bolt in for the original A6.