Found a variation between 1967-69 and 1970 C7ZA-3A652-A power steering ram cylinder frame brackets. My observations with the extra gusset are on 1970 Dearborn Cougars. Mustangs have to be the same. Just one more thing to consider when selecting parts on a restoration. Further investigation is needed to pinpoint a general changeover.
Casting number straight or curved is also a tell tale sign. There may be more differences that I haven't noticed, but here I am just sharing stuff.