What valves were installed in the head, where they SBC or application specific 6 cylinder? As 70Nova said, repeating the same thing over again and expecting a different result won't happen. You need to find out why it failed first, before you replace anything. I would start with removing one of the worst ones and looking at the top of the guide and the bottom of the retainer on that particular one you remove. The type of damage your showing is cause by the seal being pinched or crushed between those parts.
