I am a bit puzzled,,,, I just did this exact job on the 400E, about 3 weeks ago. There was a distribution block on the rear crossmember where both rear lines tap in. Took about a 12 inch line on the left, and a 20 inch line to the right, not a big deal at all. If you didn't have that block and had to route all the way to the firewall,,, what a PITA.
BTW,,, that is exactly where my brake lines failed.

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