temp sensor swap??????????????????????????

When the previous owner swapped gauges, did he swap just the gauges themselves or did he swap the whole cluster? What year GT did he get them from? This don't sound like a sensor problem, it sounds to me like the previous owner replaced the whole cluster from a GT. Does the oil pressure gauge work, if it does, what position is the gauge needle sitting at exactly? (eg .. what letter in the word "NORMAL"?). What does the voltage gauge read? And last, what indicator lights illuminate when you start the engine? I can help you more once you answer those.. then I can verify exactly what was done here. Same goes for the fuel gauge.

I did a gauge swap on my 96, from a 95GT. There are certain things you can and cannot use from the other cluster. Eg.. you cant just swap the whole cluster from a GT stang into a V6 without some modifications.