The only reason why the 1973-1974 Formula Super Duty 455 cars came wit hthe shaker hood was because of emmisson's testing, as I recall reading, the certification was done with the shaker aircleaner, and to certify for the Formula air cleaner would have been another round of testing.
In summary:
all 1970-1975 Formulas, with the sole exception of the 1973-1974 SD-455 cars, came with the same "Formula" hood.
