Which is the other manual Ian? Although it says "chassis service manual" on front cover. It appears to cover everything....Lubrication to Emissions....
I apologize for being a butinski :) but I own both.
They say 1975 Chrysler Plymouth Dodge on the cover and cover all cars including the Dart/Valiant.
One is called the chassis service manual and you are correct, it covers most.
The other is called body service manual and it covers all body issues including electrical thing such as lighting and includes wiring diagrams which have been a godsend for me. It is almost half the thickness of the chassis manual.