Doc has found a book of old pictures. He shows Marty one,

Doc: Look ... the William McFly family. Your relatives?

Marty: My great-grandfather's name was William.

Marty lays his finger over photograph of William (posed by Michael J Fox)

Marty: That's him. Good looking guy.

Doc: McFlys...but no Browns!

Marty: Look, Doc, maybe it was mistake. Maybe that grave wasn't yours. There could've been another Emmett Brown back in 1885. Did you have any relatives here back then?

Doc: The Browns came to America in 1908, and then they were the Von Brauns. My father changed our name in World War I.

Marty: Doc! Look!

Marty has found a picture of Doc in front of the "new clock" (the one that is now stuck at 10.04). It's dated September 5th 1885.

Doc: Oh! Great Scott! It's me! Then it is true. All of it. It is me who goes back there - and gets shot.

Marty: It's not gonna happen Doc. After you fix the time circuits and put new tires on the DeLorean, I'm going back to 1885 and I'm bringing you home.

NOVEMBER 16, 1955

Cut to an Indian themed drive in outside Hill Valley. Doc is preparing the DeLorean. Marty is getting changed.

Doc: The clothes fit?

Marty: (o.s) Yeah! Everything except the boots, Doc. They're kind of tight! I dunno, are you sure this stuff is authentic?

Doc: Of course. Haven't you ever seen a Western?

Marty comes out. He's wearing a pink outfit that would look very out of place in 1885.

Marty: Yeah, I have Doc, but Clint Eastwood never wore anything like this.

Doc: Clint who?

Marty: That's right....

Marty gestures toward the movie posters. One of them, Revenge Of The Creature, starred Clint Eastwood in a small uncredited role!