There were a few ratios available. It would depend on who ordered the car and it's primary purpose.
The majority I've seen were either 2.92 or 3.08. The ST-300 trans was limited in how much gear would "work". 3.55s in GTO were the "lowest" (highest, numerically) I've seen, but I don't recall ever seeing that in LeMans or Tempest. I have, by no means, seen EVERYTHING, though...(:-
On the left rear portion of the axle housing, there's a two-letter "code". Get that and check "walllaceracing.com" for what that code means. There's always the chance the gears have been changed once in the last 43 years.
Jim