I personally worry about core shift more than year casting. If doing a roller, grinding the lifter valley is a crap shoot. So to me, a roller block would carry more weight for me than a certain year casting.
Right and thing about it, casting methods only improved over the years, so the later blocks are generally better as far as not having a lot of core shift. Even though the earlier blocks can be thicker, they sometimes suffer from core shift worse than the later blocks. That's why it's always best to get them sonic tested so you know what you have.
