Vacuum lines
Ok, on the 348 with tripple two barrel carbs the vacuum advance gets it's vacuum from the hollow stud at the rear right hand of the rear carb. The 283 is the same with the two and four barrel. The 348 with the four barrel takes the vacuum from the intake manifold port just behind the four barrel carb (this is the one your looking at), For the transmission vacuum modulator tee the line and run one to the vacuum advance unit and one to the modulator.