Dan! I have treated the hole system with WD40 to prevent rust. Since the hole system is NOS it was indeed some old grease on it which has kept the systemin great shape. But I talked to some restoration shops and they all agreed upon using WD40 for protection.
Today I was able to get the hole system in Place and that felt good. On the tall pipe between the Y-pipe and the muffler I found some blue markings as well as the tejp. Remember that Dart and Valiant/Barracuda had 2" difference in lenght so I guess that was the way to make Life easier for the staff at the assembly line.
I have one question on the exhaust system. Which way was the ends on the U-bolts pointing? My idea is that they were pointing down wards. The reason would be that it was easier to use the power tools to tighten the bolts and nuts!