You can put any shocks you like on your car
C7 shocks would not be correct for a 1969 Shelby and (rear) shocks are not easy to swap out.
I dont comment on what organizations like MCA should do, thats their call.
I follow a simple rule, if the part you are using does not look like the original part, expect to take a deduction. Personally, I wouldn't knowingly pay for an incorrect part. There are currently people who make "reproductions" of original 1969 Shelby shocks.
Its all about being historically correct.
Is your car a big or small suspension car?