Fan is reverse threaded !!!! don’t forget that. As for holding it, you can make a tool for about 3 bucks. Go to lowes for something and get a thin FLAT metal rod, I used a aluminum flat bar 1inch by 3 feet I got at a hobby shop.

Anyway drill a hole large enough for the bolt of the water pump pulley to go through it. Do that about 1 inch from the one end of the rod. Put the rod over one bolt on the pulley and mark where the next bolt will need to have a hole drilled. Drill a hole for the second pulley bolt to go through. Be advised the bolts are not evenly spaced.

Tool finished. The fan clutch is not on very tight so you can almost always get away with the screwdriver or ugly stick jammed into the bolts to hold them.

Remember reverse threaded !