Impossible to add without removing the transmission. The case must be cracked open. Best to do it when the clutch is done. No special gaskets, just a tube of Ford sealant and the shifter forks. Oh and a torque wrench!!!! They are easy to install, can only be installed one-way so no mistakes.
Mechanical Skill Level = Moderate
Oh well, so much for not cluttering this post with extra conversations.
The contour V6 MTX-75 speedometer gear part # is: F5RZ 17285 AA $6.30