i gave up on simply adding the existing storage volume to a storage pool. i got up quickly with access to the previous install by restoring the lxd config.
service lxd stop mkdir /mnt/old mount /dev/OLDDRIVE /mnt/old mv /var/lib/lxd /var/lib/lxd.old cp -R /mnt/old/var/lib/lxd /var/lib/ service lxd start lxc list
i still have the rest of the install to test...