Ignition planning/understanding

You need a (free) factory service manual SEND ME A PM and I will get you one

The diagram you posted is 3rd party and leaves out a whole bunch of "stuff." It is however, sometimes easier to follow

MSD NEVER needs a ballast and works entirely different than the stock igntiion

Stock, old school breaker points, the later Mopar electronic, the aftermarket Pertronix, The GM HEI which can be adapted (the module) and the cheap China "ready to run" distributors, whether points or electronic, are sometimes called "Kettering" or "switched." The work by switching the ground leg of the igntion coil, which is usually fed through a ballast

MSD is a type of CAPACITOR DISCHARGE and like it and other CD ignitions, they NEVER use a ballast and work on a COMPLETELY different principle than the above systems. CD type systems work sorta like a camera electronic flash---a high voltage power supply charges up a fairly large value capacitor (condenser) and when triggered, discharges through the coil

Whether you want/ need one or not depends on personal preference, and HP rating. Many MANY high performance engines run just fine with something else.

WITHOUT PHOTOS just a guess is "the box" you are talking about is the VR or voltage regulator. IT has a sort of triangular 2 terminal connector, blue and green wires

The ignition box on those (factory) is normally mounted to the fender apron. Right side for stock stant six and left side for V8