I was just thinking about the percentages and how off it would be, so thanks for clarifying that. I went to Ford a while back and they want $75 to program the speedo and I said I think I'll wait.
I had a superchips micro tuner on my 2001 and I loved it, I may look into getting another one for this truck. Also on the 2001, the GPS and the Speedometer were only 1 MPH off over the entire range of speeds 5-95 MPH. I tested it!
95 was hard to sustain with out worry of getting pulled over so that didn't last long, but it read accurately. I'll start looking for programmers and see what the money flow states as to purchasing.