The 4.6L engine with a '6' VIN code is a 4.6L Windsor engine, while the 4.6L engine with a 'W' VIN code is a 4.6L Romeo engine. While the base engine block itself is the same, there are numerous differences. The Windsor engines are primarily intended for truck use and are heavier duty, while the Romeo engines are more intended for passenger car applications. The Windsor engines use an eight bolt crank, while the Romeo uses six. The valve covers and cylinder heads on the two engines are completely different, as is the intake manifold. These are just the KNOWN differences. Hope this helps.
