I would at least be sure to get the 70’ (18”) aluminum cars and not the 60’ (15”) aluminum cars when pulling with the premier big boy. Lots of sets out there, but I do know the 60’ cars (15”) were offered in a 4 car set. Think about it, the premier big boy would be longer than 2 of the 60’ cars, or half of your consist.
The OGR link below listed the UP 5 car premier aluminum set as 20-6506 and 2 car add on as 20-6606. They all have silhouettes. I have the PRR and C&O versions of these same cars. While I purchased these in the late 90’s before all of the modern remakes have come out, I still like them. While they have no interiors, I like the feel of the aluminum weight and they look better to me than the post war size aluminum cars (60’, 15” lengths). Before Covid, the 5 car set could have been found for ~$200 or less. Not sure now as train prices don’t seem to be stable and predictable since then.
