If money and parts availability were not the issue...I'd build a Cheetah any day of the week.
Powervalve, bigger intakes, better head design, bigger bore...
It's a winner all the way around.
Especially for a dune/drag bike.
You can usually find used PVs on ebay or forums for a helluva lot less than 1K....
When you build this kind of motor, don't stop there or you'll be severly dissapointed. Override or dunable override are a must for a 10 mil if you want to be able to shift well and consistently under any kind of powre.
Lockup clutch as well.
Longer swinger, more paddle, longer brake line, longer chain, gearing....
And depending on what kind of intakes, carbs and pipes you're running....that might need to be swapped too.
It never ends....