Short answer ; No, not as a Factory Option, but Yesm as a Genuine Ford Accessory that could be purchased at a Dealer's Parts Department.
Ford actually called its Reverberation System (which was actually made by Motorola) the "Studiosonic Sound System". Ford first offered this in 1962 (Part Number C2OZ-18875-C) for $22.95. In 1964, Ford replaced the 1962 version with a C4AZ-18875-A Kit (both Kits were shown for all Models, except for Convertibles), which now had an added Foot Operated Switch (identical to a headlight Dimmer Switch). A picture is attached from the 1964 Ford Accessory Brochure, I don't know the List Price of the 1964 Kit, as I do not have a 1964 Price Book, and the 1965 Price Book only shows the Part Number, as by then, the C4AZ Kit had been Replaced by the 1965 Kits. In 1965, Ford Replaced the C4AZ Kit with a C5AZ-18875-E Kit (shown for all Models, including Mustangs), and a C5ZZ-18875-A Kit, shown specifically for Mustangs. My guess is that the C5ZZ Kit had a wiring harness specifically tailored for Mustangs. Also of note for 1965, is that the Foot Operated Switch to turn the Rear Speaker On/Off, was now shown as an option for $3.75.
In 1966, the C5AZ and C5ZZ Kits were replaced by a C6AZ kit, which was forall Models, including Mustangs. There was no longer a specific Kit for Mustangs.
1967 again saw a change in Part Numbers to a C7AZ prefix, but now because of a change in type of unit. Prior to 1967, all reverberation units were mechanical, relying on springs to produce the reverberation effect. Beginning in 1967, the reverberation effect was done electronically, aqllowing for a much smaller unit.
For more information, you ma6 want to see my Article in the "Library" Secion.
Hope this helps,
Bob