I know there was another fairly recent thread about the layout of the Racer. But with the search unavailable, it was easier just to find and paste this link that was used in that thread. Scroll down to "layout." It's really rough, but if you can follow it, you'll see how to trains appear to switch.
My guess is that the original trains are either Vettel or Dayton Fun House (Like the Jack Rabbit built around the same time). Before making it's way to the History Center, the original lead blue car used to sit outside one of the converted train cars near Station Square. I actually think that I even have a picture of me sitting in it somewhere.
I could be completely wrong, but to my knowledge, one of the cars even sat on the river bank of the Allegheny River at one point. Anyone care to comment on that one?