Here's why:
* Collector Location: The location of the header collectors (where the exhaust gases merge) on shorty headers is often different than the stock manifold's outlet location. This will likely clash with the existing exhaust pipes.
* Pipe Diameter: Shorty headers typically use a larger diameter piping than the stock exhaust system. This means the connection points won't match directly.
* Ground Clearance: Even shorty headers might interfere with the steering components or other chassis parts in a Caprice.
In short: You'll almost certainly need to at least modify the existing exhaust pipes to connect them to the shorty headers, potentially replacing the cat-back section entirely (the section from the catalytic converter back). A professional exhaust shop is usually needed for a clean and proper installation.
