I don't believe the American Freedom Train was ever pulled by an FA. A PA-1 pulled the Freedom Train of 1947, but no cab unit pulled the American Freedom Train of 1976 (an E-9 pulled the Preamble Express). The complete Freedom Train is a good train to model because it only had seven cars vs. the AFT's 26. Hopefully someone on the forum can answer you value question, but if the engine is an FA then it would not be correct for either train.
Ron