From what you describe I believe that you had an under dash ammeter wire melt. These types of meltdowns are common and cause many really random problems.

If you are reasonably proficient at wiring you can repair it yourself. I used to do them all the time which is why I am now reasonably proficient. LOL

Start by checking the basics and get a wiring diagram.

Basics,

1. Are the bulkhead connectors fully plugged in and are the terminals fully seated on each side of the bulkhead. Not uncommon for the harness to have damaged terminals or the place the terminals seats is damaged and the wires move out of place when you push the connector on.
2. Voltage correct to the ignition switch and if you disconnect the switch does the voltage paths/wiring respond correctly? ie does it have open continuity to the start circuit until you rotate the switch to start. etc.
3. Is the dash properly grounded? A bad or intermittent ground will cause all kinds of problems such as the clock starting and stopping.
4. Ground the wire to the starter relay from the neutral/park switch and see if the car cranks with the key. A no crank after you messed with the neutral safety switch wiring could be a sign that a repair didn't take.

Be vigilant on the wiring harness. I have seem more than one bad diagram floating around on the internet. Typically it will say that the XYZ wire is supposed to be in position 12 and it is actually position 11 OR it will be in position 12 on the engine diagram and 11 on the dash diagram. I have also seen people move the wires from a bad connector spot to an empty one messing with the OEM pattern. My 74 RR had the wire moved by the previous owner on the engine side of he connector and when the ECU didn't fire put in a points distributor as a fix.

After the basics are covered if you choose to repair the harness this is how I do it.

1. Remove the harness lay it on a table to unwrap it. It isn't just one linear harness it has branches and random wires exiting the main harness so I use plastic ties or tape to keep the bundles grouped and random wires marked.

2. After unwrapping I check the big wires for meltdowns and look closely at any wires in the harness near the meltdown. When they melt they rarely take out 1 wire. Repair as necessary.

3. I then run my fingers down each wire feeling for weird spots. Squeeze it between 2 fingers and slide along the wire. Repair as necessary. This is important because it is real easy for damage to hide from your sight but harder to hide from your feel.

4. I upgrade the red and black wires to a larger size and leave plenty of excess hanging loose. I then run those wires through a hole in the firewall and use a much beefier connector, a bulkhead pass through or solder the wires on one side. I do this to bypass the OEM bulkhead connector. They are a weak link.

5. CHECK THE AMMETER INSULATORS a commpn problem that causes shorts and burned wires.

6. Make sure the engine side has a fusible link. DAMHIK....

If you decide to repair the harness NAPA or Amazon have lots of wire colors if needed and the packard terminals.


Or like others said buy prefab harnesses. They are easy, but not cheap.

Hope it helps.