My documentation is just my experience. The Marti of the S C6 coupe, tach as an option, and my S 4 speed GT coupe, tach not listed and it has an 8k. I have seen numerous 4 speeds with tachs, but not their Marti's.
I have also seen numerous C6 cars with the tach option called out on either a window sticker or Marti. I have not seen any Ford docs stating "all 4 speed cars get a tach". Maybe an S code only thing, which is where most of my prior interest was focused while restoring two of the beasts.
Be interested to see someones Marti for a 4 speed car and tach option.
Dealer options aside, as noted that is a can-o-worms, that requires an invoice and does not prove "factory option". As I'd bet if you had the right money you could pay a dealer to do almost anything, even "non standard" options... were these the first restomods? :wink: