Don't waste your time on fan clutch wrenches that are $25 at your local parts store. They won't fit on this truck. You'll need a 40mm to loosten the clutch nut, if you're lucky.
The pulley is no longer made and a challenge to find used.
I used my impact hammer and got mine off.

 

I bought the same wrench set from O'reilys and noticed that it, too, did not fit the nut. So I took a grinder with a flap wheel to the wrench and tweaked it until it fit. Worked perfectly. It only needs a small amount of sanding to get it to fit.


Another interesting observation made was that my new replacement water pump had thicker castings around the bolt holes, thus requiring 1-1/2" long bolts. Factory bolts weren't long enough. The heater hard line also hit my alternator bracket, so I had to bend it a bit to make everything clear.

 

Auto zone rents the correct wrench set for the 4.9. Just went through this a couple months ago.

 

my snap on air hammer gets it off, every time.

 

How do you get it off with an air hammer?

 

Myself I use a large pair of channel locks on em, works every time and one less special tool to buy/own.

 

Not a big deal to go to parts store and rent the correct tool for $25, for a job you hopefully only have to do about once every ten years. I was able to get a big pair of channel locks on the fan clutch, but could not get anything on the water pump. Had to have the slender wrenches. Heck, they give you all your money back when you take the wrenches back,