Jake/George: Paul Rudd (not sure of height)

Sadie: Robin Wright (not sure of height)

Deke: James Woods

Ellie Dockerty: Dianne Wiest

Lee Harvey Oswald: Paul Giamatti

Al Templeton: Michael Chiklis

George De Mohrenschildt: Brian Cox

Harry Dunning: Gary Sinise

The ages are probably all wrong, but these are the faces that I see going along with the characters.