I'm more familiar with full contact kickboxing which ironically only used kicks above the waist. However the fighters that crossed over well into oriental rules involving kicks to the legs were Benny the Jet Uriquidez, Rick the Jet Roufus, Maurice Smith,and Don The Dragon Wilson. With the exception of Mo Smith they all suffered losses to muay thai fighters before they learned to adapt properly to leg kicks. Maurice of course went on to win the UFC HEavyweight Championship in MMA.
Benny the Jet
Rick Roufus vs Rob Kamen
Don Wilson KO's first K1 Champion
Maurice Smith vs Stan the Man