This has always felt wonky to me, and I'm sure I'm missing the most obvious approach.

When you run make tardist (which should be the last thing to do before uploading the resultant tarball to PAUSE) it generates the META files for you (as part of the implicit make distdir) and therefore they are automatically included in that tarball. To me, that is the most obvious approach. By doing it this way I never have to actively think about any of the META files - remember that laziness is one of the Three Virtues. HTH.