I am restoring a very original '68 cuda, I am lucky- but I feel your pain. Without fender tag, build sheet or window Monroney you can't establish what the car originally had, you can only piece some things together. First off remember that starting in 1968 all major components had the VIN stamped on them- engine, trans and two places on the body. Your 150 MPH speedo was part of the "Rally" package but did not include that center gauge. That was extra, either a vacuum gauge or a tach. Cannot see from photos, do you have the "Deluxe" interior? What rear end? Case #? Start documenting what you do have. You can ask questions on specific items. Good luck.
