I have a 1980 Z28 with the 85MPH speedometer. According to what I've read I can't just change the speedometer to a 130 or 150. I'm wondering has anyone ever done a swap from the 85MPH to higher. Because apparently even the fuel guage isn't compatible. Do I have to change the circuit board and all the gauges? Because if so, that begins to get a bit pricey for a "let's see if this works" type of deal. Please help.