I did a search on the forums but can't find the answer. I just replaced the manifold and heater control valve.

Where is the source for the heater control valve vacuum for a 1971 cutlass surpreme 350? If I understand correctly it is under the dash white/grey stripe vaccum line?

I have two lines coming through the firewall. One line goes to the vacuum canister on the firewall. The other line (white stipe) goes to the heat control valve.

The vacuum canister/tank has a vacuum line coming from the manifold.

Is this correct?

 

Both the vacuum canister and the HCV lines should run through firewall to AC/Heater switches. The vacuum source is the manifold, a line should run from manifold to canister, them from canister to AC switch, then from AC switch to HCV.