First, IA64 is a completely different architecture:
http://en.wikipedia.org/wiki/Ia64
64 bit drivers will not work on a 32 bit kernel. The kernel module is not open source. It's a small open source wrapper that links to a binary blob. This binary blob is 32 bit.
If you really need 64 bit opengl drivers, the open source radeon driver from ports works on r100-r400 cards, and if you compile it from git it works on r500 cards, too.
Adam