I emerged guile-1.6.7 in order to work on gnucash2 several weeks ago.
I never had a problem with it, althought I have a small usage of Guile.
I did 'make check' in the work directory; all tests passed.
Please add the ~ppc64 KEYWORDS to dev-util/guile-1.6.7.
marking it ~ppc64 and closing. thanks for your help