I ordred mine from Greaseworks in Corvallis, OR. I bought a complete kit from them for around 80 or 90 bucks and it came with that section of line. They might sell you just that section of line, I dunno. I've heard that BD only affects rubber when there's heat involved. BUT, the rubber seal around the filler neck on mine is toast from about nine months of using BD, so go figure.

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1981 300D non-turbo 263,000 mi