There are several pieces to that line - the banjo fitting at the transmission with crush washers, the hard line, the flexible spring wrapped line and intermediate fittings. Can you isolate the leak point? If it's the hard line, chances are the rubber pad between the clamp and line disintegrated leaving the clamp to rub against the line. If so, you can get a new line ($$$), get a good used line at a wrecking yard or through the parts forum, cut the line and slip rubber hose and some clamps to fix it, braze the line, etc.

Sixto
87 300D