Since my harness has seven fuses and both my factory service and the drawings referenced above show seven, I was expecting the harness sold as "totally plug and play" would have seven as well. Seems like a reasonable assumption to me.
I think probably that the low line cars (Dart 170, 270) may have had fewer fuses. Or maybe it all depended on the options ordered when the car was built. Maybe they had a crew of munchkins making up each harness per the build sheet, I don't know.