Thanks for the responses and thanks, Jeff, for all the pics.
I wonder now if the 2 hole per side striker is the S7MS version... just thinking out loud here, maybe a prototype or the first batch of fiberglass decklids had mislocated captive nuts, and Ford ran some strikers with the extra hole under the Shelby part number to fit those, then mixed them back in the with the regular production strikers, which would explain why they ended up on regular production Mustangs too...