I did a MSD spark box (6 series) mod on my truck.........let's see........two years ago this June.
I went with the HEI hop up kit and a spark box.
I like it so far (ie:when I push the right pedal it goes forward(!))
I did it mainly to get the coil out of the distributer.....it puts too much heat on the module for me.
I next need to rid the truck of the factory distrib. with a MSD magnetic job and I will be module free (at last).
The one thing I know about those systems (I won't say how

)
is that they put out far more juice than factory ignition.