A/C Question about high/low pressure lines...Which are which?

[DamnedButDetermined]

I haven't had a/c for about two years now and it has finally gotten to the point of me fixing it. I have bought a retro fit kit to change from R12 to R134a and I have a friend who has access to an a/c vacuum/evactuator, so we can get all the old R12 out of the system. We don't know whowever which line we should hook it up to as to propperly suck all the old refrigerant out. I have a 1990 fastback and if you are looking at the compressor from the passenger side of the car you will see two service ports that lead to the compressor. The one on the right has a red cap and is leaving the compressor and goes toward the front of the car. I am guessing this is the high pressure line, because it seems to go to the radiator looking thing with the electric fan. The high pressure side is the extremely hot side correct? The port on the left has a black cap and leaves toward the firewall.

So yeah i just need to know which line to hook up the evacuator to and which line to hook the retro fit kit up to?

thanks in advance,
-DbD-