It's extremely unlikely for an undamaged original fan to cause a vibration; what's more likely is that it's the fan clutch, especially if the hole in the attaching flange on the clutch isn't properly mated to the pilot on the water pump hub. Most GM water pumps through 1970 had a 5/8" pilot protruding through the water pump pulley, and the correct fan clutches had a 5/8" hole in the flange. Many pumps changed to a 3/4" pilot in 1971, and the mating fan clutches had a 3/4" mating hole in the flange.
If you install a fan clutch with a 3/4" hole on a water pump with a 5/8" pilot, it won't be precisely centered, and the resulting vibration can fail the clutch and take out the water pump too; most clutches with a 3/4" pilot hole in the flange include a precision 3/4"-to-5/8" adapter bushing to center the clutch on the water pump pilot, and if you don't use it, you'll have vibration and major failure.
Most aftermarket auto parts store fan clutches aren't thermostatically controlled, and are junk; most of the Camaro parts houses have the current GM replacement Eaton fan clutch - that's the one you want.
