For those interested, I've put together an x86_64 kernel build of ChromiumOS for Cr-48. The kernel itself on this build is 64-bit, but the userspace is all 32-bit.
Linux 2.6.37-23105-g79d6518 #1 SMP Thu Jan 27 10:52:21 CST 2011 x86_64 GenuineIntel GNU/Linux
Just unzip, write to USB and restore using the recovery image. This is the build I'm currently running. Hope you enjoy!