Correct gas cap for 65 GS

[gs spoken here]

What is the correct gas cap for a 65 GS. The one on the left as you are looking at the picture has been on my car along time. I appears to be leaking, just old. The one on the right is off a 66 GS. The tanks for 65 and 6 are the same are the caps and is this correct. Thanks Bill

[Brian]

The one on left is correct for 64 and 65.  The one on right is the style they switched to starting in 66.  If you put the one on the right on your 65, the license plate holeder will hit the ears on it before it hits the rubber bumpers on the backup lights.