As for the actual consist, it started out with mostly all Penn Central, steam heated cars when Amtrak took it over, pulled by GG-1's from Washington to New Haven, then E series EMD diesels from there to Boston. Later on, Amfleet replaced the heritage cars, pulled by E-60's sometimes with a HEP car to New Haven, and a P-30 on to Boston. Later on with AEM-7's, and F40PH's New Haven to Boston....not sure of the years of the changes.
Anyway, it was not the 'glamour' train it had been in the PRR / NH era of the fifties, with full diner's, parlors, and parlor-observation cars....just another 'corridor train'.... The Senator - April, 1955 - Streamliner Schedules