Can someone please explain the term "roller block" when applied to a 302? What makes a roller block? I have a block that did not come with a roller cam, out of a truck around '87, with flat tappet followers. Is this considered a non-roller block? What does it take to make a non-roller a roller? Are there physical differences in the castings? I was planning to turn this into a 331 stroker, and will need roller cam, rockers and followers. Does this make sense with this block?