Unfortunately there's not a lot of new reproduction brake pedal linkage parts being made for the '71-74 B-bodies, which is surprising considering that they used basically the same brake linkage parts as E-bodies and therefore the market would be much larger for them. I guess no one has wanted to take the financial risk involved in tooling up for such parts. And if they were being reproduced for these cars they would no doubt cost a small fortune - much more than similar parts for GM or Ford cars.
As far as going to the salvage yard to find parts for this car goes, those days are long gone around here.
As much as I like old Mopars, I think my first Mopar is going to be my last one because of all the frustration I've had with this project and how much every part - no matter how small or if it's new or used - costs for them. All the GM vehicles I've restored have been much easier (and less expensive) to do.