I just changed the same line in my 97 astro AWD, the line comes from the ABS controller under the drivers seat and goes through the drivers side engine bay and does ride on the metal bumper behind the cover. Thats exactly where mine rotted out. I had a friend who had a flare kit so I just grabbed about 10 feet of line, a coupling, and bent mine into place. You wont find the adapter that goes into the ABS module at LAPS so what I did was disconnect the line from that module and take off that connector. Make sure to put it on the new line BEFORE you flare it (made that mistake it sucked) You can get the line pretty close to the original location.
There is a connection above the caliper where the metal lines mate to the rubber lines that power your caliper. Take that connector with you to the LAPS and make sure it threads into the coupling that you will need for the new line. There are 2 different size lines in these things and the connector that goes into the ABS module makes the line look smaller than it is. If you get the connector from behind the caliper you will get the right size line. Get rigid brake line that bendy stuff with the compression fittings is junk.
Also a tip: When you get the connector off the ABS module and have a little stub of brake line still in it. Put it in a vise, get a torch on it and get it red hot. Then take a punch and tap the old line out. This works well for me a lot of the time. Maybe take a needle file and just clean the inside of that connector very lightly do not remove any meat from it. I hope this helps!