[Greg Reid]

That appears to be a ported vacuum source. I'm not positive because I don't know that specific carb setup. Not unusual to have it plugged if you have no need for it. Why they would do it with a long hose is another story. It may have gone to the distributor at one point. I suspect that the line directly on the manifold right in front of it may be going there now?
The big fitting on the back usually goes to the brake booster. Where is your booster getting vacuum from now?

[corn goat]

DBL check your plug wires for the correct firing order on the cap and appropriate spark plug.coils go bad with heat .points are cheap.there arent that many things to replace .if its shaking the mirror its timing .if its a fuel problem it will act like its running out of gas .for what time it takes to run around having things teasted you could have bought a new coil fuel filter fuel pump cap wires etc.for no more than a couple of hundred bucks you will at least know what you have.1 tow bill could all most cost you that much.lastly if its shaking the mirror check your drive shaft .On my 69 i just replced so i knew what i have and i wouldnt hessitate to drive it anywhere except the gas price will kill me.good luck. p.s. minimize the rubber lenghts as everyone says and old rubber deteriates from the inside out and will collapse from the inside

[Darth Menace]

Originally Posted by Greg Reid

The big fitting on the back usually goes to the brake booster. Where is your booster getting vacuum from now?

See the picture directly below your post? See there is a fitting right above the hose I am holding. That connects to the brake booster.