Why not just pop the cluster out, remove the clear plastic and reposition the tach needle? Would take all of 20 minutes start to finish and is free.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.