The arrows show how the fuel rails would be plumbed in parallel. The crossover tube is removed from this configuration and its holes welded shut. Holes for AN fittings are drilled into the end of each rail so that an AN fitting can be TIG welded. A Y-block is required on the pressure side supplying each rail independently. Although packaging this setup is a bit more complicated, if you're making big power with your LT1, it is worth the trouble.