Yes....it's possible but the clutch fan mounts to the water pump shaft and sheave the same way but a solid drive fan uses a spacer and different bolts. It's unlikely that the water pump sheave was changed, but possible. Actually, the clutch drive fan uses less HP at high RPM, but the water pump is still turning the same RPM, for cooling purposes. IMO....it's unfortunate that the first person just didn't replace the detective fan clutch....aftermarket units are not expensive and perform well. The origional system used a seven (7) blade fan and the clutch limited the fan's RPM, but not the water pump speed to use LESS power at interstate speeds. Now, with a solid drive fan arrangement, it's moving more air than needed st highway speeds. Personally, I would have just rebuilt the leaking PS pump.....but since you still have it, its not too late to do so, re-install the origional drive sheave and retain the existing solid drive fan.....
BOB RENTON