You can download useable wiring diagrams over at "My mopar" along with some other goodies, here:
These two diagrams
There's other good stuff on that site, so browse around
Here's a thread at FABO with several full service manuals posted:
Here's a 69, but I dont remember if it's a complete manual or just the body manual
Yes, the MAD article points up the problems with Mopar bulkhead connectors
So far as the starter relay, here's how Mopar ignition/ start systems worked for years and years
The start relay on older stick cars had the coil grounded, so had only 3 terminals
The start relay on ALL automatic cars had an extra "push on" terminal for the relay coil, as did the newer stick cars which have a clutch safety switch
The big stud is one of the relay contacts, as well as a junction point
The big "square" terminal is the other contact, and goes to to energize the starter solenoid
In order for an auto or a stick car with a clutch safety switch to "crank" the extra "push on" connector on the relay MUST see a ground from the neutral safety switch or the clutch safety switch.
Here's how Mopar ignition switches work, which are in reality several switches in one container.
The power for the IGN switch comes in off the ammeter circuit (red) This is NOT fused except for the fuse link, and comes from the factory welded splice in the under-dash harness in the ammeter circuit
The IGN switch has the following SEPARATE switch circuits:
large black, hot in "run" or "accessory" feeds power to the switched buss in the fuse box for stuff like radio, heater, wipers
dark blue, hot only in "run" feeds part of the instrument cluster, out through the bulkhead to the regulator and ignition system (dark blue) On newer cars, this also feeds the alternator field, the choke heater if used, and I believe the distributor solenoid if used. This is sometimes called IGN 1
Now "start" is a little tricky
The yellow on your start relay comes from ONE PLACE, and is the IGN switch start contacts that wire comes directly from the switch, out the bulkhead and to the relay, and is hot ONLY in "start." If the neutral safety switch is in park or neutral, the relay should energize, and that will fire the starter solenoid.
But now you need a "hot spark" for start, and the battery voltage sags during cranking. So the "IGN2" or ignition bypass circuit is used. This is a separate switch, hot only in start, and is a brown wire goes directly from the switch, through the bulkhead, to the Coil + side of the ballast resistor. In effect, it feeds "hot" voltage direct to the coil + during cranking.
It is VERY important to go through that bulkhead connector and upgrade the connectors, or as I did, just run new wire through the connector.
Consider headlight relays, and even consider a relay to operate the ignition/ regulator.
You can check just how bad the voltage drop in the IGN1 (run) circuit by doing the following:
Turn the key to "run", engine OFF. Make sure the points are closed, if you still run them, by checking the voltage at the coil -- IF the voltage is high, close to "same as battery" the points are open. Bump the engine until the voltage goes very low. This helps to put a load on this circuit during your test. Don't leave the key on for more than a couple of minutes.
So now, put one probe of your meter on the battery positive post, and the other probe on either the regulator IGN terminal, or the key side of the ballast resistor.
You are measuring the voltage drop from the battery -- through the fuse link -- through the bulkhead connector -- through the ammeter circuit -- through the IGN switch connector -- through the switch -- back out the switch connector -- and back out the bulkhead connector on the dark blue -- to the regulator and ignition.
You want to see a VERY low voltage, the lower the better. If over .2V (two tenths of a volt) show concern, if approaching or over 1/2 volt, you need to find out where the drop is.
(My old Dart before rewiring had a ONE VOLT drop in this circuit.)
This low voltage makes the regulator think the battery is low and ADDS to the charging voltage by the amount of the drop.
So far as "minimum wiring" to test drive the car, though, if you have to, just simply "hot wire" it. The coil resistor should have a blue wire going to it. Confrim that with the key on, this is hot (disconnect the wire for that test.) Clip a test lead to the end with ONE wire, the other end to the starter relay "big stud." Crank and start the car by jumpering a screwdriver/ pliers across the two largest, exposed terminals on the start relay.
That should at least get the thing running for a short test hop, assuming the points, etc, rest of ignition are OK