He has spent decades relating his beer-run story, often to incredulous scoffs from friends, strangers, even some relatives. But once people saw his photos and met his soldier buddies, who backed up the tale, he said, “I didn’t have to buy a beer for a long time in Inwood.”

[It was the ultimate saloon tale: Read more about the beer run.]

Mr. Donohue finally wrote up the story in 2017 in a self-published book called “The Greatest Beer Run Ever,” written with Joanna Molloy, a former New York Daily News writer.

Now that Hollywood wants it, he said: “It’s a hoot, it really is a hoot. I certainly never expected the whole thing to get this far.”

The story was well known among members of the Sandhogs Local 147. Mr. Donohue promoted the book by doing readings at union meetings and for veterans groups.

Mr. Donohue’s story began in 1967, as he was attending funeral after funeral of friends who had died in the Vietnam War.

He was drinking in Doc Fiddler’s, one of many Irish bars in Inwood, in Upper Manhattan, when a bartender blurted out that someone ought to go to Vietnam to buy the troops a beer for their service.

Mr. Donohue did just that. He had served four years in the Marine Corps and was working as a merchant seaman. He got a job as an oiler on a merchant ship bound for Vietnam, shipping out with a duffel bag full of beer and a minimum of information on a half-dozen friends stationed there.