A body Electric Speedometere ( Auto Meter)

Cheers: I'm back from the road but need some help. I want to buy an electric Auto Meter Speedometer.
Any input would help as far as the Sensor part of it.
If anyone has installed one of these please let me know how you handled the install.

Thanks,
Gerry

P.S. I drive Truck Over the Road but try to help with other peoples questions as best as I can, Sorry for my Limited time.