To partially answer your question. All the sets I have seen do NOT have a one piece line from the front of the proportion valve to the rear end of the car. I believe for shipping reasons, it is two pieces with a union approximately in the center.
I bought my lines from Right Stuff and the front to back lines were 1 piece, with a large sweeping 180 bend in the middle that was no problem straightening out. (73 Duster)
