Rusted brake line replacement

Hi all,
I have a 1992 Park Ave, not the Ultra, and one of the rear brake lines has rusted out and is leaking. I got all the necessary supplies to cut out the rusted section and replace it but I ran into a complication. The section is just behind what my service manual calls the rear brake proportioner valve. There is one in each line in the area just below the driver's rear door. They have flare fittings on the ends and are both heavily rusted. I'm sure something is going to break once I start to work on them. I have been unable to locate any information on them or where to buy them or even if they are still available. My local Buick dearer's parts store was not open over the weekend so I can't speak to any one there till Monday. Is any one familiar with them? Could they have been used across platforms or model years? Is there any online stores that specialize in older Buick parts? I can't seem to find any doing a Google search.

Thanks,

Mike

The section is just behind what my service manual calls the rear brake proportioner valve. There is one in each line in the area just below the driver's rear door. They have flare fittings on the ends and are both heavily rusted. I'm sure something is going to break once I start to work on them.Soak the fittings overnight with PB Bblaster and you will be able to remove the fitting! Click Here (http://www.pbblaster.com/products.html)