I have a 71 charger with a 318. The previos owner installed an electronic ignition system from mopar, edelbrock carb and manifold, other than that it is stock. I just got the carb rebuilt, and the car always started bad when cold. I went on vacation and when I got back the cold starts were horrible and now it wont start at all. It is around 20 to 30 degrees farenheit where I live right now. Im pretty sure I have air and fuel because i have a clear fuel filter and my carb is newly rebuilt. I tried to ground out a plug wire to see if I have spark but I saw nothing. The cap and rotor look reletivly clean and there is about 11 volts running through the coil and ballast resistor, and the plug wires are in good condition.  

has the car ever performed properly? do you have a 4 or 5 pin module. Checked your ballast resistor? 2 prong goes with the 4 pin module and the 4 prong goes with the 5 pin module. Test the resistance of your coil with a multimeter against a good/new one. see  http://autorepair.about.com/cs/troubleshooting/l/aa062902b  for a reference.  

try dumping a little gas down the carb .if it does'nt start or at least stumble  its ignition