easy solution to wrong speedometer gear issue..make your own speedometer display.
i used an iphone app to tell me my speed then made a mark corresponding to needle position on the speedo glass at 10k/h intervals. i then transferred those marks to a piece of tracing paper which i scanned, uploaded to my pc and then photoshoped before printing it out on a color printer (adjusting the scale until it was the correct diameter). even added a little chevy logo i got off the net. cut center hole out and then put it behind the glass in the original display. works a charm, and passed inspection
https://drmike.smugmug.com/Other/Truck/i-GfhTGGB/Aps if you dont have a scanner you can just hold the tracing paper to the pc screen and copy the design using MS Paint through it