I would recommend keeping to the 1.5 ohm coil and the correct OEM type of ballast resistor versus the 3 ohm coil. The reason is that when cold, the original type ballast resistor will be low (around .5-.6 ohms) and the charging current into the coil will be higher and will give more spark energy for better cold starts. Once operating, then the ballast warms up and its resistance increases to a bit over 2 ohms and the coil current reduces to normal running levels (that of a 3 ohm coil alone).
This is the way the original system was designed to work, for better cold spark energy. It will also compensate for extended high rev running, if the average dwell drops and thus coil current drops; the ballast resistance will lower and compensate for that to some extent.
The trick is to get the right ballast resistor for this. You need to find one that is near to .5-.6 ohms cold and a bit over 2 ohms hot. And OEM ballast does this, and MSD sells one that is .8 ohms cold. The BWD RU19 is around .6 ohm cold and about 3.5 ohms hot so is a fair replacement, but a common ballast sold to many folks (RU4) is 2 ohms cold and 7 ohms hot. No wonder people have ignition problems that go away when they change to a no-ballast system; the wrong ballast will lower spark energy big time. Don't listen to the parts guy when he says "don't worry, it will work"; I finally ran in to one parts guys who actually knew the resistance difference in a Mopar ballast.
BTW, I changed to a 1.5 ohm Flamethrower coil and cold starts are much better with that and the proper OEM ballast resistance. (I bought an actual NOS ballast.) But I suspect the old coil was getting weak so I am not certain that the Flamethrower is all that much better than a stock coil in good shape. The spark voltage ratings are 30-35kV for the original, and 40kV for the Flamethrower.
