i bought an 02 road king police bike fuel injected that had been wrecked.the wiring harnes had been cut when all police lights and sirens were taken off so i decided to change all controlls to standard road king.i replaced the wiring harness with an 05 road king. everything pluged in with no problems except for speedometer. i had to purchase a different speedometer. well it does not work, when i go slow the speedometer registers up to 120mph. i decided to take to harley place and they said they could not reset ecu to axcept this speedometer and they want to sell me a new wiring harness and i would have to find my old speedometer to put back on. now to my question does anybody know if i could put on a newer ecu and it work with my other components?i know it would work with the speedometer but would it work with fuel injectors and crankshaft sensor and etc? seems like it would because everything works now except speedometer and it does throw 3or 4 other codes that i dont know what they are. can anybody help?

thanks, james