In the KVM, attach the debian ISO to the CD drive. create a disk image with a couple megs in disk utility, and mount it.
pull down drivers from a working x64 box of the same kernel version as the installer:
(right now, <sys> is 2.6.32-5-amd64):
in /lib/modules/<sys>/drivers/scsi
libfc/libfc.ko
fnic/fnic.ko
put them in the disk image.
attach the disk image in the KVM manager alongside the ISO for debian install, and run the installer until it gets to the part where it wants to partition your disk. you'll see the boot LUN disk is not listed (it only lists your disk image). hit Go Back and you'll go to the menu.
go to a terminal session in the installer (start a shell session)
mount the disk image (mount /dev/sda /mnt) (you may need to specify VFAT if you do this via Windows)
copy the kernel modules into place:
cd /lib/modules/<sys>/drivers/scsi
mkdir libfc
mkdir fnic
cp /mnt/fnic.ko fnic/
cp /mnt/libfc.ko libfc/
Load modules
depmod -a
modprobe libfc
modprobe fnic
exit terminal, go back to detect disks stage. you can continue normally from there. When GRUB wants to set up the master boot record, say no. Then, tell it to install to /dev/sdc. Then life will be kosher.