You seem to refer to this post
According to Giusti it was (ex-)Yugoslavia too. He quotes an interview with Caltabiano, who talks about his experiences in former Yugoslavia.
Personally I think too it was filmed overthere, the town looks like those towns in the Winnetou movies and Yugoslavia can be quite dry. The entire region (South-East Italy, Croatia, Albania) is known for long, dry periods, alternated with periods with a lot of rain. Furthermore it’s an Italian-German coproduction, there’s no Spanish involvement. Yugoslavia was the German Wild West, so to speak (the Indians were immigrant workers)”
Maybe Pistoleros had scenes from both Croatia and Sardinia 
I have no screen shots available though but at least those common with Pecos Cleans UP then should be from Croatia.
Very interesting that your posted screen shot from Django The Last Killer was from Sardinia.
And further relatad complications might be that some movies even could have reused distant shot riding scenes from other movies .
How, off topic, was it about the last scene or so in Sabata (as Aldo mentioned several years back) when the guy riding doesn´t look like Lee van Cleef but maybe just any Spanish local guy/caballero used to perform at their ferias, and maybe not taken from another movie.
The Feria Rosario each October in Fuengirola (where I stay in the winter season) always have Horse shows with those traditional dressed men with a ceartain stiff back riding style
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