Making the best of a bad situation

They're full of crap regarding different pedals for power and manual brakes. That's a big NO. They are the same. They probably told you that because they couldn't figure out how to get the pedal up on it. ........BUT remember, power brakes will have the pedal fall further down when the engine is running, because the booster is activated. How far down can you push the pedal without the engine running? That will give a good indication of whether the problem is hydraulic or not. That also looks like a A body booster "to me". But as inertia mentioned, as long as a booster fits, the application doesn't really matter. As for the shop you used, I'd find another one. Better yet, get a factory Chrysler service manual for your car and learn how to do it yourself. It's not difficult. At least that way, you'll know it's been DONE.