85 to 140 speedometer ?

do you really want white faced gauges in a mustang? send em to brothers, they'll slap a 170 face on it with the factory look, and recalibrate it for a good price.

You need a real 140mph spedo, try finding one on ebay. The new one will bolt right in and then you can replace the "sticker" for the white face gauges and it will read correct.

Do a search on speedometer and you should find more info, but basically, you have to either have your existing speedo recalibrated by a speedo shop (it's not an easy fix with a gear) or you have to get a real 140 speedo that is already calibrated. The speedo reads the number of cable turns and translates that to your speed, so by changing the face you still need to chage the mechanism.

The 89 was the first year of the 140 speedo stock. A 89 speedo will fit right in yours. In 90 they changed the cluster around and it is not a direct fit. You can get a 90-93 speedo only, not the whole cluster, and just use the actual mechanism behind the face in your cluster. You unscrew the old 85 speedo mechanism from the clear plastic face that the white face gauge cover is glued to and put it on the new 140 speedo mechanism and replace the needle.

Good luck!