It’s amusing that you mention Eastwood. If you are thinking of spaghetti westerns the sound wasn’t really recorded when filming (actors were using multiple languages anyway) and the movie was dubbed on studio by the original actors or someone else depending on the output language.

“There was a crude “guide track” recording what was spoken, but often Leone lost or ignored this guide track and when the time came to loop the dialogue, frequently no one could remember who had said what. Eastwood recalls being warned to keep his OWN NOTES about what he said in each scene, and sure enough, when he was called on to loop the two Dollar movies, production had lost the guide track. They had NO IDEA what Clint had actually said in each scene and Clint had to re-record them as best he could remember. (Another reason why his lip movements don’t entirely match up.)“