Did the 55 Nomad have dual exhaust on the power pack?

No - they did not. In 1955 station wagons did not have dual exhaust for the wagons with Power pac. In 1956 they modified the gas tank to allow room for the tail ppe on the right side,

I had an article pertaining to this in the G&D a couple years back.

Nonetheless, I presume many folks put duals on the PP 1955 wagons. And also on the original 2 barrel cars that were changed to 4 barrel manifold/carb. I can see why. Duals with Smithy type mufflers on those small blocks is a real 'sweet' sound to my ear.

A good buddy in our region has a nice '56 210 wagon. Still quite original; except for the duals. When he pulls away from the house, etc - man, what a "cool" sound!!! Definitely takes me back to the day!