Inline Tube dual master cylinder conversion

Has anyone purchased the three piece line set and the distribution block from inline tube for single to dual reservoir conversion? I'm trying to wrap my head around how the lines are routed. The photo of the block looks like there are 4 ports. Does the rear line go directly to the MC or the block? If you've used this kit please be as detailed in explaining what line goes where because I'm confused.

Thank you.

66 Dart, all drum brakes.