A full cut of Back to the Future featuring actor Eric Stotlz in the role of Marty McFly isn't possible. The 1985 time-travel classic is beloved today for its brilliant script/story, hilarious plot, and roster of perfectly cast actors, including the great Michael J. Fox in the lead role of Marty. However, the role was originally inhabited by an entirely different actor: Fast Times at Ridgemont High's Eric Stoltz.
As is common knowledge today, Stoltz took on the role early in production, and shot a number of the film's most iconic scenes. However, one month into the film's planned three-month shoot, the decision was made to fire Stoltz due to his incompatibility with the role. The actor was quickly replaced with Michael J. Fox, and every scene involving Stoltz was subsequently reshot.
In the years since the film's release and worldwide success, audiences have often wondered if a full version of Back to the Future starring Eric Stoltz as Marty exists. Some have speculated that such a cut might exist within Universal's vaults, buried and intentionally kept out of circulation. However, while multiple shots and scenes showing Stoltz in the film have surfaced in documentaries and online over the last few decades, a feature-length "Stoltz Cut" of Back to the Future has yet to surface. The reason for this is simple: no such cut exists.
As mentioned above, Eric Stoltz was fired from Back to the Future one month into shooting. This means that only a third of the film's three months of principal photography was completed with Stoltz in the role, so even if a cut of the film staring Stoltz existed, it would only constitute a third of the whole film. Thanks to the brief amount of Stoltz footage that has surfaced, it's confirmed that he shot scenes including Doc testing the DeLorean time machine, Marty's arrival in Hill Valley, Marty meeting his father, Doc getting the idea to power the DeLorean with lightning, and the bar fight with Biff. That still leaves a number of iconic and vital scenes unshot, and when director Robert Zemeckis did shoot them, it was with Michael J. Fox in the role.
Even if a complete "Stoltz Cut" did exist, it's doubtful that it would ever see the light of day. Instances of alternate versions of films being released are few and far between, and when they do happen, it's usually only due to overwhelming fan demand. In addition, Robert Zemeckis and Back to the Future writer Bob Gale have always been incredibly protective of the trilogy's legacy, and while releasing more of Eric Stoltz's Marty footage could happen one day, an entire second (potentially inferior) cut of the film would almost certainly be out of the question.