Again I'm just trying to answer your question as to why the rear brake line came up short?? I still believe the line that you show is correct for factory 1969 disc brakes (B41 on the fender tag). A factory four wheel drum brake car doesn't require any proportioning value in the rear line so therefore a slightly longer line is required. This is what 1969 engineers designed not me. Until it was pointed out to me and I looked at the FSM I was unaware about any difference. On another note the rear wheel cylinders are also different part# from factory drum or disc. If my memory serves me one is 7/8" the other 15/16" ??I figured I ordered it for drum brakes instead of disc (the factory line for the yellow car (came factory with disc brakes) went all the way to the P-valve.
Regardless keep on doing what you're doing cause you're doing a great job. Like your co-pilot by the way.