You can find some more information on what happened to Santa Fe's Hi Level El Capitan fleet at
http://www.trainweb....angab/hilev.htm . In particular it has information about the disposition of the Diners, which apparently never got any Amtrak re-numbering.
The
Super Chief in the heyday was a sleeper only train, and was low level. It was the Coach only
El Capitan that was Hi Level. In the waning years before 1971 the two trains ran combined as a single train called
Super Chief - El Capitan, with a Transition Car connecting the two sections together.
The double-decker sleepers in actual realization are an Amtrak innovation, much as it is hard to believe
Yes, El Capitan was indeed a high level train when Amtrak took over in 1971.
But it was originally a low level train (the only kind there was!) when it was first built as a new streamliner in 1938.
It received a big dome probably in the early 50's. Then in 1955-56 was re-equipped as a high level train, coaches, diner and lounge. In 1963 there was a new order for more high level coaches (though not diners or lounges).
At that time the original high level coaches were placed on the San Francisco Chief,itself a new schedule made of hand me down low and high level cars.The CAP got the new coaches.
And some time afer all that, some of the high level coaches drifted over to the Texas Chief.
About the Super and the CAP running together, that was an on an off thing for awhile but it eventually became permanent. It was kind of seasonal at first, like running as separate trains in the summer, still.