Heritage Fleet consisted of all-electric rebuilds of passengers cars from the 1940s and 1950s that previously used steam. Amfleet has always been all-electric.
E units and SDP40F's were assigned to steam cars. F40's and P30CH's were assigned to electric cars.
The Palmetto, which began in 1976, used Amfleet and ran behind a P30CH into the 1980s.
E units were gone from the NY-Florida trains (Silver Star, Silver Meteor, and until 1979 the Champion) by 1976 or maybe 1975. Those trains were pulled by SDP40Fs in the late 1970s. The Silver Star was the last train in the east to convert to Heritage Fleet, so it would still have been using SDP40Fs in 1980. The Silver Meteor might have been partially or completely converted to Heritage Fleet by December 31, 1980, so there is a chance that an F40 was used on the Silver Meteor in 1980. The Champion was discontinued before it could be reequipped with Heritage Fleet.
And don't forget the Floridian, which ran Chicago-Florida. In its final year, 1979, it ran behind an F40/E8 combo. (The E8 provided steam to the cars.) This train never received Heritage Fleet. The F40/E8 combo replaced the SDP40F which had pulled the Floridian after 1976, except for the brief period of time when the Floridian was combined with the Auto-Train and was pulled by Auto-Train U36B's that were accompanied by a separate steam heater car.