He finished in the top ten twice, with his best finish in 6th position in 1982 at Riverside. In 1979, Leffler was the USAC Sprint Car National Series Champion.
Leffler's accomplishments include finishing in the top ten twice, with his best performance being a sixth-place finish in 1982 at Riverside.  In 1979, he secured the USAC Sprint Car National Series Championship.