I’m trying to replace the water pump gasket but as I’m unbolting the fan clutch two of the studs spin as I’m trying to loosen the nuts on them. Other two nuts came off fine. Really don’t know what to do about it and I need some suggestions, 1986 22R if that matters.

 

Replacing the water pump gasket only? Why? If I were to tear it down that far I'd for sure be replacing the water pump as well. Probably all the hoses & thermostat too.

As for the studs they look pretty dry & I see a bit of rust on one of the ones you did get the nut off of. Get some penetrating oil/spray on them & let em soak a bit & try again.
If the threads have rusted away on the studs where the nut is sitting that could account for them just spinning. You can try wedging a small screwdriver behind the flange & try the nut again. That might move it just enough down the stud to catch the threads.

You could also Dremel a slot in the end of the stud & try to back them out of the clutch hub.

Beyond that if none of this works I just split the nut with a cold chisel to get them off then go get all new hardware.