New water pump 6 impellers whats up with that!

I was going to use the six blade but the 8 came in today. It looks the same as the one I pulled off. It is a Cardone Part # : 55-33118. So Im going with it. As you can see in the picture the new one is visibly deeper. Bolt holes measure same with caliper and width and depth of blade sightly larger.

Thanks Craig