Educate me on ballast resistors?
That's good information to know. The one post on here says 0.5 - 0.6 ohms is best. I checked my ballast resister from Summit and it is stamped 1.25 ohms. Is this too high?
For most stock and stock replacement coils, yes.
What coil do you have? Exact model is needed, including a PN if possible. I'll venture to guess, based on the behavior of other ballasts, that the 1.25 ohms cold ballast will rise to about 5 ohms hot, and the coil current (and thus spark energy) for most coils will be low with that. The most common original Mopar ballast is a bit over 2 ohms hot.
You'll be somewhat better off with most coils with a BWD RU19 ballast from the box parts stores than the 1.25 ohms cold one; you will be getting closer to what the system was designed for. High ballast resistance can/will effect warmup situations from a cold start; the engine will run great for 10-30 seconds and then get a bit rough for a while until the engine gets good and warm. High ballast resistance can also effect high RPM firing.
One common ballast I see on a lot of cars is 2 ohms cold and 7 ohms hot; that reeeeally effects things adversely. Below is a pix of the 'bad one', the one with the rounded mounting tab, and the better BWD RU19, with the angled edge mounting tab. As noted before, the original Mopar is best with a stock type coil; it has the correct resistances cold and hot that the Chrysler system was designed for; my /6 ran pretty much perfectly in cold Jan starts with the original Mopar ballast, the RU19 was decent but a bit rough, and the cold start went to crap with the RU4.