Vacuum line for heater

[k51977blazer]

Where do you guys attach this vacuum line to, I wanted to put it in the correct location.
1976 k5 blazer
350

 

[Capt Ron]

Manifold vacuum behind carb.

 

[k51977blazer]

Vacuum reservoir {round plastic thing right above heater hoses

it’s attached to that where does it go from there wasn’t sure if it connected to the intake or carb

 

[k51977blazer]

Thank you