"ENDLESSLY." Dizzy Gillespie. Impulse 42153. Every few years some bright producer decides: "Let's do something to make Dizzy sell records." So here he is complete with DX 7, programmed strings and songs by everyone from Stevie Wonder to Marvin Gaye. Perhaps because he enjoyed meeting the challenge, he plays exceptionally well. Forget the pop vocal on Kristofferson's "For the Good Times," and the dismal doubled-up arrangement of "I Should Care." At its best (Horace Ott's "Tippin' In" and Clyde Otis' "There You Are") the presumptive objective is met. 3 1/2 stars.