That looks like it ought to work. Have you tried
using --with-python *without* giving a path? If your path
is such that the fink version of python is gotten first
(e.g., if you type "which python" and you get something in
/sw), could you try temporarily changing your command search
path such that it does not search /sw/bin ahead of /usr/bin?
I'm wondering whether --with-python without any path
arguments will work for you when it finds the MacOS python.