An engine at any stage of build. You can buy a short block. or a long block with the heads and oil pump already installed, or you can buy a complete engine ready to switch with yours. It appears that the sellers have the economies of scale and their sale price runs about the same as your parts price for each stage of the build. My cousin the engine builder explained that every partial build he has seen had problems. Including Mr. Goodwrench. They come from an assembly line with unacceptable tolerances both in clearances and in torques. Every one he has ever bought needed to be torn down and everything retorqued to specs.