Check this:
(I'm reading through the 1971 Factory Pinto Car Shop Manual, in the ignition section, shortening what they say and paraphrasing. If it seems completely at odds with what you see in yours, good luck.)
Anyway, according to the text, yes, the actual running voltage used in the ignition system is reduced by means of a RESISTANCE wire placed in the circuit between the ignition switch and the ignition coil. This circuit is active when the ignition switch is in the RUNNING position, but is bypassed while the ignition switch is in the START position, ths applying full battery voltage for easier engine starting.
In cases where the engine will start but will not run with the switch in the running position, the resistance wire should be checked. (I think that it makes sense to check it even though yours isn't bad enough to have a serious running problem-yet.)
To test the wire, connect a voltmeter so that it spans the gap when you disconnect the resistance wire coming from the switch, where it attaches to the coil. Now run a GOOD ground wire from the DISTRIBUTOR side of the coil to a GOOD ground.
With all accessories and light off, turn the ignition switch on.
If the voltmeter reading is between 6.6 and 4.5 Volts the resistance wire is ok.
If the voltage reading is greater than 6.6V or less than 4.5V, replace the wire.
The problem then is to find a correct resistance wire or resistor and to replace the existing one, which may not be easy to do, because of how the old wire is an integral part of the wiring harness.
In this 1971 manual they are telling you to drill a 1/2" hole in the dash panel (for access) 1" to the left of the centerline of the pad retainer grommet hole and 1" above that same holes' centerline, which puts the new hole on a diagonal between the large squared wiring hole and the pad retainer grommet hole.
The way that they present it, it's fairly involved, but the basic idea is to cut the red/green stripe wire on one side of the main connector, and the red/yellow wire on the side of the ignition wire connector (which is on the steering column, in the passenger compartment), attach BOTH the cut ends of each color wire to a service wire replacement, and then pass the new wire through the hole that you just drilled so that you will be able to connect it.
They go to great pains to tell you not to use anything but the service replacement service wire, and not to loop the resistance wire against itself due to possible heat problems from it's resistance, but I would assume that as long as it is the correct resistance any appropriate resistor could also be used instead if this "special" wire, with it's custom ends, (one of which is removeable, to allow it to pass through the hole, and meant to be used with bullet connectors), is not available.
The part number that they give for the service replacement is: C9AB-12250-A.
After that is done, then they want you to cut the No. 16 PINK wire near to the printed circuit connector, and insulate both of the cut ends, to isolate the old wire.
I should say that the wiring colors are possibly going to change from one year to another, but the actual bypass technique and connector placement involving this circuit would most likely be similar, if not exact.
A couple more things that they mentioned in this section are:
If the voltage regulator is set incorrectly, it can cause excessive pitting of the points.
Ditto if the radio condenser is installed to the distributor side of the coil .
Ditto if the igniton condenser is the improper capacitance.
Ditto if the engine is operated for an extended period of time "at speeds other than normal", whatever that is.
