If you get one of those Abbott ERA boxes Electronic Ratio Adapter (ERA) you can use the signal from your ABS and trigger the ERA box to adjust the ratio for the speedo to read correctly. It has dip switches to allow proper adjustment. This is how I did it prior to my 6R80 conversion and it worked flawlessly.Damn, wish I would've known this before I turned my front abs sensor into the speedo. My speedo is off by about 10mph. Can I fix that with my handheld? Or I may just wire it up like you explained.