All right lets break it down to a few more simple steps.
Find out the correct voltage YOUR coil should have at the positive terminal with the key "ON" (NOT CRANKING the engine). Measure this with a quality volt meter (digital is best). Within range, move on.
IF possible find out the specifications for the OHMS resistance of YOUR coil. Measure this with your meter, within range, move on.
Measure the OHMS of your coil wire, TRY to find out what "OHMS per foot" is spec for your wires. Measure your plug wires also. Within range, move on.
IF your distributor trigger device does have an "air gap" spec, find it and measure it and make it correct. Move on.
Examine carefully your "rotor bug" UNDERNEATH for signs of burn through or shorting. Check the cap for black "arc" trails. Check the wire connections for loose or INTERNAL BREAKS. I've seen wires that looked good on the outside (insulation in place) and were broken INTERNALLY (rare). Measure OHMS while wiggling wire.
Does voltage STAY within range as the car warms up or revs up? Is the spark good at idle AND higher rpm?
...sheesshh, I could write a book on this.
