Glen, the back tube doesn't go to the distributor, it connects to the black rubber hose that goes up the the top of the carb. It's purpose is to supply filtered air to the heat tube in the exhaust manifold that then goes to the choke coil on the carb.
If you need the steel line, just buy some brake line tubing and bend to fit. The carb fitting can be found in the plumbing supply at your local hardware store.