I've found golf tees to work great for plugging the fuel line! I've used them on my '70 but haven't tried them on my '78 which I think has 7mm ID instead of 5mm ID fuel lines. It should still work though since the golf tee flares.#2 Pencils work well too. I have also used thick shaft Phillips Screwdrivers too. Just tightened the clamps back down on the screwdriver once inserted into the hose.I like the petcock idea best.
-- ------------------------------------------------------- Lee Dronick, San Diego California Proud owner of "Mobilia", orange '76 Westy www.dronick.com/mobilia