More than likely the wiring is there as GM probably only used 1 wiring harness back then for all the cutlasses.
Depends on what year Cutlass Supreme you're referring to...
If your battery was dead and you jumped it to get it started and the gauge shows your not charging you need to replace the alternator.
i have 1991cutlass supreme v6 my digtial gas gage stuck
Most likely either a bad float in the fuel tank or defective gauge
I believe it was 1966 and 67.
If the gauge is reading hot and the car is running normal temperatures, the water temperature sensor needs replaced.
The cause of the faulty fuel gauge is probably the fuel gauge sending unit located inside the fuel tank. Replacing the sending unit would require dropping the fuel tank.
Check your cylinder pressure with a compression gauge. The gauge will hook up to your spark plug openings.
The color of the wire going to the fuel tank sending unit from the tank level instrument on the dash is taupe (or light tan). 1970 Olds Cutlass SX
It takes a special gauge to install the crank sensor. It can be rented from some parts stores.
check the coolant temp sensor
I have same. It runs around the the first third 0f the gauge. It has tow package. I live in Utah and temp gauge stays same all year.