Quote - I am getting a stretch mark/line on one side of the neck. Can I fix that with the texture, and what if someone loads another texture with this character?

I'm not sure it's the same thing you're describing in the above quote, but it looks like the edge of the head, where it welds to the neck, may have been moved in places.  You can get rendering or display artifacts when the child (head) weld vertices have been pulled away from the parent (neck).  This can often be fixed by using the 'Smooth'  feature of Poser's Morph Brush at a low setting.  (Or with some similar tool or process.)  That might remove the stretch mark you're seeing.  (Note that if this is the problem, altering the texture won't fix it.)

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Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.