I don't know which gas cap is correct for a 1948. The original GM accessory locking cap with the GM script on the locking flap is hard to find and very expensive. The article in the post above shows an original one with box. On EBay a NOS GM cap in box would probably be 500 to 700 dollars. They were repopped for a short time, but the repops aren't cheap either. All these rare accessories are expensive due to the lowrider crowd collecting them.
