the vac line runs from the rear of the heater control switch through the firewall/bulkhead and connects to the inlet manifold.
the image below shows teh vac line connecting to the inlet manifold. bottom one.
Do you have a picture where does the main vacuum line connect to the blower's vacuum line in the firewall?
I need to replace the missing vacuum tube from the T-joint to the firewall, but I don't know where it connects to.
Sorry for my broken English