Why don’t you describe the changes you see between frame z139, z144 and z150 and give us your sense of where [the limo's passengers] are all facing?
In Z-139, JFK, who has been waving to spectators on his right (but not yet to Mary Woodward and Co. who are further down the street towards Zapruder), has begun quickly turning his head to his left in Jackie's direction. He looks in that direction for about a second and then, by Z-160, starts turning his head back to his right. By Z-175, he has turned his head far to his right and has started waving to Woodward and Co.
In Z-139, Jackie is already looking somewhat to her left. By Z-144 she starts turning her head farther to her left and "maxes out" in that direction by Z-161 when Robert Croft "captures" her with a concerned look on her face.
Around Z-139, Connally, who has been looking to his right and who heard Oswald's first shot less than a second earlier, turns his head even farther to his right and then, at Z-150, starts turning it quickly to his left and is "captured" looking "straight ahead" in the Croft photo. Then, around Z-165, he starts turning his head to his far right in a vain attempt to catch a glimpse of JFK over his right shoulder.
Nellie, who has been looking more or less straight ahead, begins turning her head far to her right by Z-144.
Kellerman, who has been looking more or less straight ahead, begins looking to his right/down by Z-148.
What else would you like to know?