Slant Six Racing Manual?

Does this document look familiar to anyone? I was cleaning up files on the computer today and completely forgot about it. I downloaded it in 2019 but have no context from where. Looking at the metadata it seems to have been created as PDF in 2005... Very cool document - any ideas? I posted a FULL DOCUMENT PDF HERE if anyone wants to download and review it's thorough 51 pages!

:::Sample pages below:::

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