But as an example neither include PySequence_Fast which is in the json.c changes I pointed to. The folks doing the auditing of stdlib do have an idea of what they are looking for, and so would be best suited to keep a list (and tool) up to date with what is needed.
A list of Issue and PR URLs that identify and fix free threading issues would likely also be of use for building a 2to3-like tool to lint and fix C extensions to work with CPython free threading nogil mode