The story is from Variety:
Set in Los Angeles in March 1957, story follows Fellini's first voyage to America to attend the Oscars, during which he went missing for 48 hours and barely made it to the ceremony. Pic postulates what might have happened during those two days, after which the helmer returned to Italy and directed his two most revered films, "La Dolce Vita" and "8 1/2."
Script finds Fellini discovering the jazz and surf scenes and falling for a veterinarian while his wife tries to drown her sorrows by cavorting with Ricky Nelson. Howard will play a jazz musician who introduces Fellini to his world; Macy will play Fellini's publicist; and Dinklage will play the vet's lover.
Interesting stuff and sounds like a real project, but also looks like a lot of it will be fiction(alized).