[A930Rocket]

If your going to backfill them, I'd use ladder wire between each course and fill the cells with mortar, grout, etc. The weight of wet soil can blow out a wall easily depending on it straight length. Your pouring a footer for these as well?

You also might want to try your local block plant to see if they have any seconds or irregulars. They are sold at a substantial discount. They might be grey, but you can paint or stain the wall until you cover it with stone, etc.