Front brake line pictures?

[Jakes-66-K10]

I'm ordering brake line for a disc conversion on my '70 CST/20. Here is the junction box that's on the truck now. It basically splits the left and right front lines, and that second line that does not go into the box goes across the crossmember and hooks up to the rear brakes.

What do the '71 and '72 trucks use for this junction? I'm not sure what lines to buy because nothing seems to fit what I have on my truck. I'll be using a '72 3/4 ton master cylinder and prop valve. I was thinking all I needed were brake lines down to this junction box. I'm hoping to use the existing rear lines.

Can anyone post a picture of how brakes are routed on their 71 or 72 3/4 tons?