99 Gt Speedometer And Tachometer Issue

[Wilson4812]

Hoping someone can help me out here.

Last night I installed a reverse glow gauge overlay and now I know for sure the tachometer is not reading correctly where my rpms are at and my speedometer is only slightly off. What do I need to do to fix this?

Thanks in advance

 

[wmburns]

Courtesy of Suek here's how to calibrate for a needle swap.

http://www.newyorkmustangs.com/forums/how-to-recalibrate-your-gauges-t7574.html