The first friggin result in Google with the search "GTA IV speedo"::smash3d:
http://www.youtube.com/watch?v=fMFawVx8Ssk
http://www.gtaforums.com/index.php?showtopic=389609
Tho I haven't been able to get it working. Dunno why, maybe I just don't know how to use the Asi loader...