Thinking more on the AMTRAK E-8 set, it does limit prototypical operation to New York - Florida trains. The one-off scheme not withstanding, the patched SCL units seemed to stay in Florida service in 71 - 74 era. The slides I have seen show the units mainly in Florida pulling the Silver Meteor, Silver Star, and may have powered The Champion.
Western early AMTRAK trains used ex-UP E-8/9 units or the new SDP40 for long distance service.
Of course in our condensed 3-rail world anything is possible and created.
Now I need to find the Lionel AMTRAK red nose versions from a few years ago to make some fun "Kodachrome" era passenger trains.