Replacing Drums and Shoes on 69 Dart

Chrysler Master Tech series had a booklet and filmstrip which may give you some more things to look for
Drum Brake Service Highlights (Session 260) from the Master Technician's Service Conference

Look at the locations of wear on the lining material.
For the shoes, the metal 'frames' should have an FMSI number stamped in them. That's the standardized number for that shoe.
1968 introduced shoes with tabs to reduce the wear on the backing plates.
1969 introduced a new selfadjustment system and reversed the direction of the adjusters compeared to previous years.
That's about all I can think for tips at the moment. The booklet covers most things mechanical.
Hydraulic issues could be collapsed or plugged hose.