Closing the case: I removed worst part of steel fuel line from tank forward, about 4 feet. At that point original line appeared to be in good shape. I made up new steel line from tank to remaining line (using 2 pieces including 4 double flares) and double flared the existing line to hook up to the new one. Flare on old line leaked due to rough interior weld preventing leak-free connection to inverted union, so I cut off final flares, made a slight bubble with double flare die, and used high pressure hose and clamps for final hook up (as per Tinkerer).
Thanks all for interest.