oldbluetruck,
I used lengths of copper wire to test several different ways of running the lines. Even then, I scratched my head for a few days before settling on the routing in the picture. Most likely it is not as it was originally run (Fred T - thanks for looking for a diagram/picture - post it if you are able to find it).
On a 1/2 ton truck with standard fuel pump, the fitting on the intake manifold is a hex-sided plug with with a 2-3" pipe/tube that is bent at a right angle and directed towards the firewall. A rubber line/hose was originally used from the fitting on the intake to the wiper motor.
The vacuum line fitting on the intake manifold in the picture came off an intake manifold from either a larger truck or a truck that had a dual-action fuel pump. Some of the larger trucks had metal lines with flare fittings.
I agree with you that you should be able to find a brass or steel fitting to use on the manifold. Most likely you will not find a single piece to work but a reducer/adapter-or-two should do it.
Tim
