The Floridian was moved several times in order to find a useable route across Indiana. The Penn Central was rapidly falling apart in those days. I think at some point either the Floridian or the Cardinal (or one of its predecessors) was routed on to a C&O line that hadn't had passenger service since the 1930's. I do believe the Floridian also made some runs on the old C&EI north of Evansville.
The Penn Central was in such sad shape that freight trains would derail while standing still due to the deteriorating track conditions.
In the beginning of Amtrak service, both the Cardinal and Floridian predecessor trains started out from Chicago's Central Station as Penn Central trains, using their 'Big Four' route trackage rights on the Illinois Central mainline until just north of Kankakee. Then stopped at the Big Four Kankakee station, and on to Lafayette and Indianapolis. The Cardinal continue on the former NYC to Cincinnati, thence to the C&O to Washington and Newport News (splitting at Charlottesville).
the Floridian ran on the former PRR to Louisville, then the L&N and SCL to Florida's east and west coasts.
It was the Cardinal that moved over to the C&O of Indiana freight line, completely bypassing Indianapolis from 1974 until 1986, via Peru, Muncie, and Richmond, In. to Cincinnati. They later altered the route to serve Hamilton, Oh. In 1986, they moved to the current route.
Meanwhile, the Floridian also moved off the Big Four, and used the former route of PRR's South Wind, from Chicago to Indianapolis via Logansport. When that route got too bad, they shifted all over the state, including the C&EI via Evansville for a while. Finally they settled on a route using the former Monon via Lafayette and Bloomington to Louisville, also bypassing Indianapolis. The only train left serving Indianapolis was the National Limited. The Floridian and National Limited ended at the close of the '70's, but the new Hoosier train began serving Indianapolis also using parts of the former Monon....