MSD coil installation

Yes, you need to keep a ballast with the Mopar ignition. The MSD ignition system has some control over the current in the coil; the Mopar system does not have that control and the ballast provides some control/limiting and improved cold starting.

And, unless you have a genuine OEM ballast, do yourself a favor and buy one of the MSD 0.8 ohm ballasts and use that. It is the closest to the stock that I have found; stock is 0.5-0.6 ohms cold. Higher ballast resistances are commonly installed in the mistaken idea that a ballast is a ballast (WRONG!), and a high ballast resistance will cost you some serious degradation in coil spark energy.

The plug gap can be set wider IF the spark system will support it. With your setup, all you can do is try at .040" and if it runs good through all conditions and all RPM's, then try at .045". Typically, it takes a high energy or longer spark system (like HEI) to properly fire a .045" gap under all conditions. If you don't want to mess with it, then stick with the standard .035" but there are very real running benefits to opening up the spark gap, in economy and combustion efficiency, consistency and smoothness in firing, etc. Read up on a topic called 'spark kernal' if you want to learn more.