1973 Dart brake failiure

By 1973 more cars were equipped with disc brakes so Chrysler started using disc / drum master cylinders on manual four wheel drum cars. It was a gradual process and took a few years to complete the change on all cars.
This was easily accomplished by using residual valves in both front and rear ports.
Also wheel cylinder expanders were being widely used by this time so there really was no need for residual valves.
Some of the aftermarket companies continued making the old style manual drum master cylinders.
In the 1973 parts catalog the all drum manual master cylinder was #3580209.
Here's a photo of the 1973 master.

https://www.ebay.com/itm/3888154317...xYf67/lDqqj/UYzt0+3zbeRA==|tkp:Bk9SR9jq5_rBZw