The early blocks do not have the front cover alignment dowels. What you need to do is center the seal on the crankshaft. We do this by using an allen wrench that just fits between the seal and crank all the way around and then tighten. be careful it will move when it is tightened. If the allen wrench fits the same all around you are good to go. It may or may not line up well on the bottom where the
oil pan goes. this is jut production parts for you. The later blocks used a dowl in the block and the front cover was machined with a hole in it so that the front cover would side over the dowl. I think they got a lot better on their front covers and bock work when they did this. Just center on the crankshaft and you will be fine, this is what the seal runs on.
Good luck, Keith