Can anyone tell me which specific version of the Sherman is depicted in the film, 'Kelly's Heroes'? Is there any small-scale kit that would be a good match for this version?

Check the website 1/72 Shermans.

http://www.172shermans.com/

You'd want a M4A3W. The Yugoslavian ones are postwar rebuilds with a 76mm gun in the 75mm turret. You'd only have to change the gun barrel and leave off the front travel lock. The loudspeaker is up to you.