Jason: That's one of the things I learned in programming class MANY years ago. "Write the program assuming the operator is an idiot. If they are, the program will catch/prevent their mistakes. If they aren't, they'll never notice the difference."
The same goes for assembling products. If there is only one way to put it together, it can't be done wrong. If there is more than one way, somebody will screw it up.
Of course, that won't work if there is more than one CORRECT way to do it! In the case of the trucks, it's reasonable to assume that a prototype MAY have had more than one type of truck, at some time, so the trucks almost have to be interchangeable, allowing the wrong trucks to be used.
I ran into the same thing on a recent purchase of Intermountain 60 ft flatcars. I bought 2 of the latest HTTX cars, with plans to use at least one for kitbashing. They looked nice enough that I decided to put one in service as-is.
As far as I know, all of their earlier runs had MT trucks, or clones of them, with 33 inch wheels. These have a new truck, with metal wheels, that look good and roll well. But the car sits higher than the earlier ones, and the couplers are too high. I finally took the trucks off and installed MT trucks. That solved the problem, but why would IM make a new truck that sat too high?
It turns out that while the trucks look like 70-ton trucks, they have 36 inch wheels, raising the car about 1.5 scale inches, just enough that the couplers didn't want to stay coupled to my other cars. Since these are 70-ton cars, why the larger wheels? I don't know, and suspect that the factory grabbed the wrong wheels.
I could have put 33 inch wheels in the IM trucks, but didn't have any handy that were the right length. I've saved the trucks, in case I need them somewhere else.
Incidentally, the Atlas trucks, removed from the RBL discussed here, look more like the ones on the car I hope to kitbash, so I used those on the second flat. They also put the couplers at the right height. So, all of the Atlas parts have now been used.
