You can use each drive's UUID instead. Use the blkid command to find each drive's UUID and then replace devices in /etc/fstab and in /boot/grub/grub.conf with the UUIDs. See the posts Re: KDE 4.2 Dolphin automount NTFS on boot
and Re: mount exitsting removeable hdd
for examples for /etc/fstab; see the post Re: No sound for AC97 soundcard
for an example of using the UUID in grub.conf. For grub.conf the kernel needs to be built using genkernel with the --disklabel argument in order to use UUIDs (see root=UUID=
and the SL Wiki article on rebuilding a kernel using genkernel), although it may already have been built that way for the LiveDVD (I'm not sure, but it certainly used to be, and you can try editing grub.conf to see; at worst you'd need to boot a LiveDVD in order to be able to edit grub.conf on the HDD if the real_root=UUID= doesn't work).