vacuum amplifier-'73 dart sport../6

Confusion confusion.

The vacuum amplifier is used to operate the EGR valve. One hose goes to ported vacuum on the carb, one goes to manifold vacuum on the intake and the third goes to the EGR by way of a temperature vacuum switch located either in the head adjacent to the temp sender or or in the radiator tank. They were used at least as early as 1973 because my Valiant has one.

It's job is to boost the vacuum signal to the EGR valve and also diverts the vacuum signal from ported to manifold at WOT.

Unfortunately you won't find one new. However you should be able to plenty of good one by posting a want ad here because that's one of the first things to go when people want to "clean up" the engine bay. I have one somewhere but I'm keeping it until they are rare and I can sell it for a lot of money like other people do.

The tank circled in the pic ain't it. That's the vacuum reservoir for the Heat and air controls. Power brakes don't use a separate reservoir.