[CentOS] Repair grub GPT/UEFI?

What does it take to make a disk bootable on a system with UEFI and a GPT on the boot disk? I used a default disk layout in the initial install on a 600Gb drive (on a box that also contained a larger raid). and it used a GPT.

ReaR won't work to back up/restore this system, complaining about the UEFI. I cloned the drive to a different server with clonezilla-live which completed without errors but it won't boot. I booted an install disk in rescue mode, did a chroot to /mnt/sysimage and everything looked OK. A 'grub-install /dev/sda' did not give any errors and I can now get it to boot to the grub> prompt. What's the right way to fix the grub install here?

-- Les Mikesell lesmikesell@gmail.com