Right Bret -
The Sumpter Valley used Vulcan trucks on many of thier 36 foot flats in the 76000 series. The correct answer has less to do with the trucks (as some of ours have SVRY Vulcans under them).
John Lewis and I had an interesting conversation about this a few years back. The 76000 series cars has archbars or T-Bentandorfs or Vulcuns. They also had 40,000, 50,000 aand 60,000 load ratings. My theory was that the load ratings had primarily to do with the truck type. John thought that wasn't correct.
I'm loath to disagree with an expert like John, so does anyone else have a theory? We pretty much know that, of the 200+ cars in the 76000 series all had 4 truss rods and all seem to have had 4x12 pine side beams. What else could there be?
Lon Wall
Trainmaster SVRY