Booting from different hard drives

Hello, I'm attempting to boot from multiple hard drives, with one hard drive having one installation of RHEL and the second having another. Virtually all of the help online covers dual windows-linux boot, almost nothing covers this.

I thought it would be simple to add a second option to grub.conf and point it at the second disk, but that has not proved to be the case, ala

title Rhel1
hd(0,0)
kernel /vmlinuz-version ro root=/dev/sda3
initrd /initrd-version

title Rhel2
hd(1,0)
kernel /vmlinuz-version ro root=/dev/sdb3
initrd /initrd-version

but it has proven elusive; when attempting to boot the second option grub complains that "file not found"

Any suggestions?