Hi Ray -
With our old Chryslers, it is important that we gain an understanding of how they work. In this case, it's the brake system.
Don't expect for a second that your mechanic knows or cares. They are just guessing. One thing they are good at is draining your wallet. I know people that have spent thousands of dollars on mechanics trying to get 1950s Chrysler brakes to work properly. And all they get for their money are some marginally working brakes and a boatload of excuses ("they were never any good" etc).
Guess what ? They do work and are good if they are set up properly.
So as the owner of this fabulous vehicle, it is incumbent upon you to become the expert. You do that by reading the Factory Shop Manual. It's all explained there. Also, on MyMopar, you can read the MTSC booklet and watch the filmstrip on your brakes:
https://www.mymopar.com/downloads/mtsc/125.pdf
This is what I had to do when I did the brakes on my car back in 2008. Once you read/watch the above, you will find the answers to your questions and be able to identify the root cause of your issues.
Ron