In 1997 Chevrolet replaced the most successful American V8 ever built with a clean-sheet design that shared almost nothing with it but the layout. The LS1 brought an all-aluminum deep-skirt block, six-bolt mains, cathedral-port heads, and coil-near-plug ignition, and it became the default swap engine for an entire generation. Here is what changed, where the stock parts run out of room, and the unglamorous details that end fresh builds early.