Hustler mower just clicks

The Denso part number is for the starter less the Bendex & pinion gear.
The Briggs number if it has one includes the above items.
There are two different sized gears 14 & 16 teeth.
If the power supply to the starter is low then it will not be able to force the starter to engage with the flywheel.
This is an AMPs problem , not a Voltage one so you need a clamp meter to test it.
OTOH get a good battery and jump directly to the starter.
I like to put the + on the starter first then hook the - to the oil drain plug.
If the starter engages & spins the engine then your problem is in the mowers wiring.
If not then have a good look at both the starter and the teeth on the flywheel.

not sure what the bendix looks like on my gxv530 honda engine. over 250 cranking amps so don't think that is a problem. As i indicated before if I turn flywheel just a little it cranks right up.

OK you can disregard the previous post.
You have a throw out solenoid starter.
Only 2 reasons why that will not engage.
Buggered coils/contacts inside the solenoid .
Insufficient power available.

Other things like twisted or distorted mountings but generally it is electrical .
Grab your car / truck battery and jump directly from it to the starter as mentioned before.

Water gets inside the heavy power cables on ZTR's and the wires corrode away to nothing under the insulation.

Thanks ok do I disconnect the postive from battery to starter solnoid and the negative that goes to fuse then to starter before jump starting? Wiring could be issue since the mower is 8-9 years old.

No, leave the mowers wiring alone.
Hook the + up first because when the circuit is completed you will get a substantial spark, which is why you use a solenoid in the first place.
It is all too easy when this happens to jerk and put the lead directly on the starter case thus dead shorting the battery.
If you shake a bit making the ground contact it does not matter as everything around the drain bolt is also ground so no chance of a short.
If you want to start the mower, turn it on first then jump the starter.
I do this a dozen times a week to start customers mowers with flat batteries