Nice images! very informative: thanks for posting.
In 'Mud & Dust' I record that at least two of the early pattern PECO Earth Augers (post hole diggers) on 4x4, and 6 of the later Pacific Model 250/20 Earth Augers on 6x6 chassis were sent to South Vietnam. The booms visible in the image above indicate these are 6x6 versions. Page 278 of M&D has a rear view of one of the 4x4 versions.
The three transit cement mixers are also well covered in the text of M&D, as well as in two images, one demonstrating the inherent instability of this vehicle type (page 201).
Mike C