1973 dart sport brake booster

Hey there.

I have a 73 dart sport factory power brake car and I’m having issues with my booster.

I do not have a video currently, however maybe someone can guide me in the right direction. I was idling the car after putting the transmission back in, and I lost brake pressure about 80%. The moment this happened, my rpm went from around 800 to 2k or higher.

Sounds like vacuum leak to me. I plugged the vacuum line from the booster, to the intake. I have some brakes, but currently no power assist. The idle stayed calm and steady about 700 to 800 rpm.

So my first question, is my booster shot?

And if so, do they sell rebuilt boosters by them self?

I’m aware they sell booster and master cylinder combos, however these are for cars that didn’t come with power brakes from the factory.

Thanks for the help.