To specifically answer your question, yes, the MTL heavyweight 6-wheel trucks will fit under the car with minimal effort. The GN car that is the closest match to the ConCor baggage had 6-wheel trucks also, so I put a set on one model in the past.
Now, to go off on a tangent, depending on how much work you want to put in...
http://rrpicturearchives.net/showPicture.aspx?id=576409There's a better shot of the trucks. They're more modern than the MTL trucks and have additional appliances outside of the frame. I'm thinking a closer match would be the Des Plaines Hobbies 6-wheel SP trucks that are available separately, but made for the triple-unit diner.
The car also strikes me as being of Union Pacific lineage... and Laser-cut sides are available to use in conjunction with an AmLtd core kit to do the UP 85' baggage cars. They're pretty easy to use for a baggage car!