If you can spin your fan freely after shutting off a hot engine, then yes, it sounds like your clutch is shot. That could be your whole problem.
If you have a non-thermal, it's controlled by rpm's. At idle, the clutch is locked up, and provides the most pull on the radiator. As the revs go up, the clutch begins to disengage, as you don't need a solid, locked up fan at highway speeds.
If you have a thermal, then you'll see a curly spring in front of the clutch. When temps get hot, the spring engages the clutch, and the fan is locked up. As the revs increase, the thermal clutch behaves like a regular clutch fan, and will nearly freewheel at highway speeds.
Not sure of the factory fan will bolt up to the Hayden clutch. I bought the Hayden 18" black fan when I bought the clutch. Been using it for many years now.
A rule of thumb on your current clutch fan:
- When the engine is cold, and the engine is off, if you can flick a blade with your hand, and the fan spins more than 1/2 a revolution, the clutch is starting to go. If the fan spins an entire turn (or more), then the clutch is shot.
- With the engine hot (at idle), shut the car off. The fan should stop immediately. If it continues to spin a few revolutions, the clutch is shot.