Help me understand rebuild vs crate?

"Crate engine" is a very complicated subject. The original "crate" engines were factory assembled with all new parts including the block, heads. Now everybody uses the adjective of "Crate" engine to describe their assembled engines, with no guarantees as to the actual quality of the package other than their personal claims. There are the Mopar factory "crate" engines GM "crate" engines and then there are a million others. Like anything else, DO YOUR HOMEWORK !! And remember this always, " The quality is remembered long after the price is forgotten."