If they aren't painted you can heat them with a hair dryer and pull them off. More than likely, it will be a SLOW process. With the age of the stripes they will likely come off in small bits. But they will come off. After you get them removed, use some adhesive remover or gas on a rag and clean off all of the glue. Wax and enjoy your stripe delete GN
You should be OK with the process described, but if not, you can buy a wheel for a hand drill. It's made out of rubber, like an eraser. It takes the pinstripes and glue right off.
Depends what the car is painted with. If original lacquer, you could carefully wetsand them off with some 600 or 1000 grit. If painted with enamel or urethane, you could do the same thing. Also, the stipes may come off with lacquer thinner. The lacquer thinner won't affect the enamel or urethane finish.