The default is a translucent texture.
The archive has an opaque original, so you can change the transparency to your taste, or not use it at all.
Edited speedometer position.
At 16: 9, 1920x1080 looks adequate; I did not test it at other resolutions.
Installation:
Copy the SpeedoIV folder and the SpeedoIV.asi file to the main game folder.
Turn on / off the speedometer in the game by pressing F5