Hoping for some wise advice.  My '72 Torino Base, 351C-2V sat for a couple of months while I had fuel system overhauled.  Negative battery terminal was disconnected the whole time.  Carb Rebuilt, fuel tank cleaned pressure tested and sealed.  New sending unit, fuel pump and filter.  Flushed the lines.  Hooked everything back up and fuel is delivering to carb just fine, but I have no spark.  The coil is getting 12V from the battery, When I put ignition switch to accessory voltmeter reads 5.6V.  Tried it with brand new coil and got the same readings.  My buddy thinks that with accessory on we should be reading higher than 5.6V and suggests there is a ballast resistor line somewhere that might be bad.  I am puzzled how something can just spontaneously go bad since it started fine before I did the fuel line.  We tested spark directly from the coil to the plug and got no spark so it seems like there's something not right before the distributor.  Any thoughts?  Is there a resistor somewhere on the vehicle and if so, where it connects?  Any suggestions on where one might be bought?  Local auto parts store lists a ballast resistor cable but says it is no longer available.  The picture they had doesn't look like anything I can see tracing the wires

Thanks!

Another item, Check the voltage directly at the battery. if it's not at least 12+ volts, trickle charge for a few days to bring it back up. if it's 10 volts or less, could have a bad cell. I have had batteries that are older drop a cell or two from sitting and age.