Unless you're the original owner, there's no telling if the brakes have been modified by previous owners until you inspect them. Email Spiegler asking them how to measure the brake lines, then go line-by-line collecting the measurements. Send them to Spiegler and ask if they have a kit that fits those measurements; if they don't, they'll fabricate some.
Rear brake line length was changed by BMW when a section of metal brake line was removed. Sometimes front calipers receive fluid by separate lines from a Y-pipe; sometimes they receive fluid via a direct line from the master cylinder to one of the calipers then through a metal pipe bridging the fender from that caliper to the other.