Slant Six Build Ideas

One interesting thing you could do that would improve fuel economy and make it faster than stock is to turbo it. As long as you do it right; i.e. lower compression than usual, gapped rings, balanced internals, you could have a fun, reliable engine. Also, you could hide the turbo down by the oil pan and just run a secretive charge tube back up into that emissions tube that goes into the snorkel. In order to keep it stock looking.
or just make a high compression slant and efi.