K-Line Heavyweight Passenger Trucks vs. Atlas Replacement Trucks - They Are Different

Lionel I understand got most of the K_Line stuff you could try use Lionel trucks or possibly MTH trucks.

The Atlas Premier 6-axle trucks are MTH tooling.  Atlas Trainman 6-axle trucks that were used on their 60' cars are a different mount.  They might work, but they aren't available for separate sale and Atlas has not run those cars in a while, especially after purchasing rights to the MTH tooling. 

I would agree that Lionel and K-line trucks are very similar.  I would need to have dig a little to put two side by side to see how close they really are though.  Purchasing a car would likely be your best option and then you could sell the remaining parts or convert the truck less car into a yard master's office which was a fairly common practice for heavyweight cars.  

Johnathan mentioned the Atlas truck in the Trainman Line. From Atlas part site.

Williams may be another option with their Madison cars. As far as the pin for the roller mount coming in contact with the metal floor. A thin piece of styrene glued to the floor may solve that.