Is there a way to "Shrinkwrap" part of a mesh and have the rest of it "autofollow" transforms?

I have a bunch of good looking low poly hair that someone did for one of his old games and gracefully permitted me to use them for mine. Except that my head is a bit different than his, mine is anime-style, his was cartoon style. Plus the whole scale issues.

So I was wondering if I could shrinkwrap the “cap” then the hair meshes would “auto-follow” the “shrinkwrapped cap” transforms.

See if this works: Assign the cap vertices to a vertex group, then use that group in the shrinkwrap modifier. If the hair itself is a separate object, you can parent it to the cap and it will follow it.