Typically for late 60s.
A is Battery outputs (and recharge).
R is Alternator circuits. R6 is alternator output.
J is Ignition and engine.
J1 is often power to ignition switch
J2 is ignition (includes power to voltage regulator)
J3 is ignition feed when key is in start.
Q is Accessory feeds
Q2 is switched accessory feed - (pretty much everything which requires key on other than ignition)
L is typically exterior Lighting
H is usually Horn.
RWO are the letters Chrysler used in the books for the mid size Plymouth and Dodge models. So the way to read the 18DBL next to (16DBL-RWO) is that Darts and Valiants will have 18 ga wire and mid size models will have 16 ga wire.
Example of a schematic made from the factory diagram with some of the wire codes.
View attachment 1715842240
Chrysler pamphlet about reading and using the diagrams.
1968 Electrical Wiring (Session 247) from the Master Technician's Service Conference
and the accompanying filmstrip.
1968 Electrical Wiring Filmstrip MTSC (Session 247)
Master Technician Service Conference - Chrysler's Training for Mechanics