on 67s the resistor wire runs from the plug on the firewall to the coil, but if your using the msd ready to run dist and an msd blaster coil or similar you may be able to replace the resistor with a regular wire to get a hotter spark

drvmarch- if you want to measure the voltage at the coil to see if you have a resistor wire the car must be running, you will get 12v either way if the car is not running but the key is in the on position

bruce1223- the wire might be for a tach if it is on the neg side of the coil, if its on the positive side, someone took power from that for something that was added. and if you take out the resistor then you can remove the wire to the starter