I really hate to be the wet blanket, but (with a few exceptions) slant-6 hotrodders are people with no money (yes, there are still questions about "how to adapt a 2 bbl."), and the idea of a $7,000 300 hp motor kills the entire project.
Just my 2¢?
The slant is so close to the GM and Ford V6 engine displacement (231, etc.) that the obvious choice is an Eaton M90.
