Vacuum lines for factory AC

[Lawdogg298]

Hey guys. I have been scouring the internet for help with vacuum lines and have so far come up empty. I will lay out my questions separately. Any help would be greatly appreciated.

Truck info: '71 K10 with 350 V8, Edelbrock 1406 carb, TH350 automatic trans. I bought the truck in "running condition" so the PO ran the lines. I recently installed a painless wiring harness and am now trying to piece together the last bit of factory AC

1. Currently all four Vacuum ports off the carb are used. Timed port to distributor, PCV port to PCV, Manifold Vacuum to trans, Power brake port to brakes. -- Where should I "T in" the vacuum hoses for AC/reservoir?

2. I have 2 vacuum lines starting off the master cylinder, running down the frame (see pictures). Top tube is fuel line. Middle one runs to the rear brake, but the bottom one is open to atmosphere. Where is that third line supposed to terminate?