Okay. So, I just recently bought a 1966 Coronet 440. She ran perfectly up until Friday. I turn the ignition and nothing happens. No turn of the engine, no clicks, nothing. The previous weekend my husband and I had taken the car to his parents' house to work on, and, while he and his dad were working on the distributor, a nut fell in. Could this possibly be the problem? And, if so, how can I remedy this? If not, what other options would I have to look at as possible reasons for the car not starting? (Yes, it has gas. Yes, the battery works fine - all of the lights are lighting up properly. And, yes, it appears that all the cables are in their proper place.)  

Does the engine turn over either by the starter or by hand? if so pull the No#1 plug and wire and ground it by the electrode and see if you have spark, am sure you know that all a car needs to start are fuel, air, and Spark if all these are there it should start but if the engine is sized won't turn over, or popped a piston or have burnt valves, So i would also do a compression check that will tell you more i hope this helps take care  

In addition to the above, the engine needs compression. But I think this is a different type of problem.

I'd start by checking the neutral safety switch and it's wiring. The neutral safety switch is on the transmission and grounds the starter relay so it will operate properly. Sometimes the wire breaks or comes off, and nothing will happen when you turn the key.

Check this first before proceeding.  

Turn on the key and check the voltmeter. If it registers anything like 12 or so volts then the voltage meter is fine; the Dodge voltmeter in those years are true ammeters and are in line with the ignition system. If the ammeter does not register anything then you will need to bypass the ammeter, but before bypassing your ammeter check the ballast resisitor as they are also part of the ignition sysytem and if it is burnt out then the vehicle will not run either; ballast resisitors are cheap. To bypass the ammeter you can do it one of two ways:
1. put a jumper wire across the poles of the (ammeter) voltage meter that is mounted in the dash. This can be alot of work.
2. run a large #8 BLACK wire from the positive battery terminal across the engine ( threading around power steering pump and thermostat) to the "battery" terminal of the alternator. This essentially bypasses the ammeter; I know this because it is what I have to do as my ammeter has failed.

Good Luck!  

Get the bolt out of the distributor!
Then fiddle with the rest.  

And did you check to see if the battery cables are clean and tight??