Started working on a '68 Dart 270 that I hung up and neglected about a decade ago. It's got a 273, 904, and manual 4 drum brakes. I noticed before I stopped driving it that I'd periodically have to adjust the rear brakes because they'd start dragging and heat up. Never investigated any further.

Fast forward 10 years. Now I need to replace the master cylinder (leaking all over, no pressure). Problem is the piece that's installed looks different from those online or at the parts stores. From what I've seen the replacements have a single bolt going into a flat metal cover over two square chambers.

The one I have has two identical humps and a wire holddown over two rounded chambers. Looks more like those on manual disc Darts or '71+ Darts with manual drums. It looks better but I'm wondering if the previous owner installed the wrong one. Are they supposed to be interchangeable? Could that have been my problem with the rear drums?

I found some threads on folks upgrading their brakes to disc or power but I'm trying to keep it stock. Only reason I'm asking is because if I replace the mc with the "correct" one then I won't have the proper core for exchange. Not a big deal ($15) but thought someone might know if it makes a difference. Thanks for reading all of this.