When I first got my '82 LS, the fuel wouldn't shut off with the fuel tap in the 'OFF' position .
The rubber washer inside the tap, had developed a groove between the holes from the metal disc that rotates when the handle is moved .
The plastic inlet tubes were broken, so I went to a hobby store and got some brass tubing, opened up the holes in the tap body so the brass tubes would fit and applied a bit of fuel resistant sealant to keep them in place .