Dart center cap.

The entire wheel needs to come off- then the center cap can be removed by removing the 3 machine screws that hold it on from the rear of the wheel.
FROM THE FACTORY left hand lugs were only used on the driver's side of the vehicle- regular right hand lugs are on the passenger side.
BUT, after all these years many have been switched out and are all RH thread (mostly due to the unavailability of replacement LH lugs). I have also seen where front brakes got switched side-to-side and have them reversed...
Usually, you can tell a left-hand lug nut by the groove or notches cut into the circumference, which designates left hand threads; or may be marked in some other fashion.
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With open face nuts, you can also see the end of the lug, which will be stamped with an "L"".
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Either way, proceed cautiously until you confirm what they are- don't just try to blast them off with an impact or force them with a 4' pipe on a breaker bar; you'll just snap them off.
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Read this at least 2 or 3 times.