KXDINO is correct.
A re-spring and valve would make those work far better then stock.
The only thing I would do different is get the setup from Pro Action rather then Race Tech.
The reason?
They are about 100 per end cheaper and they do the exact same job.
Also, Pro Action has thier shim stack already set up.
You don't need to measure and stack all the shim pieces yourself.
Remove the old valve, install the new one.
Ready to roll..
And I am a Race Tech dealer
Here is some pics of Sean Collier on his 01 KX500 with some 08 KX450F forks that we re-valves and sprung with the Pro Action set up.
Sean says that it is one of the nicest fork and shock setups he has ever rode.
I've said for years that nothing... nothing at all, will make you ride faster then getting your suspension set up correctly...