I'm quite sure IMDB used to have Stallone as uncredited actor in this (meaning it would have been his first role) but the info isn't there anymore (if it ever did) and obviously IMDB does have false info.
But, I have seen a bad quality photo of Stallone in some sort of mexican bandit outfit with some unknown (at least to me...) guy who was also dressed like a bandit, and I remember the person who had the photo to claim that it was from the filming of this particular movie. ???
Anyways this was years ago and I didn't really know the person and I don't have the image saved anywhere so... I did ask about it at the Stallone forum somewhere (which seemed to be the most popular forum around) later on and got no answer about it.
Perhaps the photo was from some other movie (what?) or something. I don't know.