1976 K20 a/c Recharge Port

[Shtudwn]

I have a 1976 K20 that appears to have been converted to 134a. Well at least that is what the little sticker on the Accumulator/Drier says.

There are two threaded schrader type ports on the Accumulator/Drier and one in-line of one of the hoses. None of them have the 134a quick-connect adapter. The in-line fitting has the two-wire switch connected to it.

Where do I attempt a recharge of the system? I have an adapter but the three locations gives me two too many options! haha

Thanks.