The Cummins Mid-Range Engine Plant is located in Columbus, IN. , off of I-65.
You will have to get in contact with them to find out about tours of the plant. The tour of the plant is WELL worth the time. It's very interesting how they build these engines.
I'm sorry that I can't help you regarding getting in contact about the tour. I suppose getting on their website would be a good start.
Good Luck with your search. You will, definately, enjoy the tour.
Joe F. (Buffalo)