New Car: My 1964 Plymouth Valiant

So here is something curious I just noticed about my car this past weekend. Check out the front fenders!
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Gas gauge never worked when I bought it and after testing the gauge I determined it was a stuck fuel sender. Coincidentally I put a new locking gas cap with a good seal on it on the car and the proper seal on the tank caused enough pressure to cause a leak at the sender (the spout). So, ordered a new sender and installed on Monday. No leak now and gauge works. I accidentally broke the ground strap taking it off but the gauge still reads?
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