Please have a look at the video below. It shows a spark fat on my pinto. What could cause this? Sequence bottom to top is 1-3-4-2. 1 and 2 seem to be intermittent and 3 does a double spark.

http://www.youtube.com/watch?v=O-UhlVSLCB0

Note video is slowed down.

The earth the plugs are getting sitting on a painted rockerbox can't be ideal?

Assuming you are still using the distributor, then leakage within the distributor cap could cause this, or possibly even an incorrectly fitted/broken rotor arm that is pointing half way between the HT terminals when a spark occurs.

Points or electronic dizzie ? ------ if points check the points cap on all 4 cylimders also check the condensor is correctly fitted and the screw holding it to the base plate is tight.

If your using a Motorcraft distributor with points and a black box on the side then bi pass the block and make up and fit a short earth lead to fit between the points securing screw and one of the baseplate to distributor securing screws to reduce the voltage drop across the points and improve the spark