The brake line lengths for my 1990 W124 turned out to be :
tee to rear left: 17 1/2in.- used 20" line
tee to rear right: 33 1/2in- used 40" line
tee forward: 117 in.- used two 51" lines plus one 20".

I used 2 NiCopp CNE-320 lines, one CN-340, 2 CNE-351s.
In forming the lines, I started with the section going over the differential forward, formed my line to the old steel line and found that I could not get it up and over stuff without a lot of hand forming as I went along. Eventually I just handformed the end I was inserting first and formed the rest of it as I went along. Not as pretty as the old lines but they worked. The excess lengths I formed around and behind stuff which didn't move or got hot, making sure that wherever it might be touching or crossing metal edges I put rubber hoses around them. In other spots, I tie-wrapped to other stuff to keep the new lines from vibrating.

Thanks for the Matco reference. I will follow these lines to make sure there is no vibration against metal objects since these lines are probably a bit more vulnerable than steel. If they begin to fail, I know what to do next.

I appreciate the history about these lines. I have no history working on metal brake lines and this whole area seemed a huge mystery. Reading the comments above got me moving toward a solution. And, it all (including flex lines) cost under $100. Thanks again