Obviously any coil will perform better with that MSD 6al box. When using an MSD box on a ford I hardly ever buy a new coil. The MSD box ups the voltage to the coil and turns it from one spark to multiple sparks for the same crank rotation.
Obviously a better coil put in place of a factory coil will perform better. But to optimize performance then yes, the MSD box is needed.
But any aftermarket "booster" ignition system will be great. Jacobs and crane make good ones also.
One last question then is would I need the 8.5mm MSD wires or will a good set of replacement motorcraft or Accel wires work? Going from 8mm wires to either the MSD 8.5s or Accel 8.8s more than doubles the price.
I'd think you would want wires (ie MSD or Jacobs or Magnecor) made for the higher voltages provided by the aftermarket ignition boxes. Regular carbon wires will wear out quicker. Wires made for the purpose won't break down over time. Wires themselves won't make any more power, the higher quality ones just handle more voltage and last longer. MAGNECOR Race Wires: WELCOME TO MAGNECOR! has some good information on this issue.
I tried out a Jacobs ignition box and ultracoil, got no appreciable mpg gain. I don't know what a dyno would reveal, however. So, I'm back on the factory coil. I'd get an MSD coil if the original one died, it's comparable in price to the oem coil.