IF that worked no one would compile on their 64bit systems and it would be a news event of biblio proportions. It would be on http://www.linux.org
on the main page!
But seriously I haven't heard of it. Sorry.. I'd just try a test with something non-critical and see if it worked and then go from there. If it does work you'll make history. Please remember this place and post the HOWTO in the Linux Tutorials section if you do figure out a way.
There's also http://www.x86-64.org/
and if it aint there I'd download a new distro that is completely 64Bit and wait for the rpm's to catch up to the system, etc.