Reply to "71 Pantera spark comes and goes?"

So I finally got back to the 71 Pantera, started checking out the suggested issues, coil, Ballast resistor and Alternator. the alt. had grinding sounds so I took that down to NAPA and found out the alt. was not charging, so I replaced that, now I have a solid 12v during idle but still only runs for 15 to 20 seconds then stops ...no spark, I am believing / hoping the coil is good because it is new and was installed at the same time as the new distributor, I know its been suggested that the ignition switch could be a source of resistance and may need cleaning or replacement, but removing and cleaning seems just a little intimidating...so that leads me to the ballast resistor, the one in the car appears to be an Autolite original, where can I find one? or what can I use? looking at the simple less expensive items 1st before I hit the switch