My 68 standard has been retrofitted with a 9" rear, posi, with 4.10 or 4.11, whichever is the correct Ford ratio. C4 tranny, 3 speed, so I'm assuming 3rd is 1.00, if this isn't right, it's due to my ignorance. The car runs around 3000 or 3200 at highway speed, but the speedo is WAY out of whack, I'm sure due to the fact that the car was stock with a 3.00, 8" rear. Is there an intelligent way to go about figuring out what little plastic gear to use in the tranny to make things OK again?? Is this a painful ordeal to change out? I've done it years ago to a GM unit, but have not, as of yet, been as intimate with the C4. Ron.