Yes I have the correct gas cap for the 351 Cleveland, It has the bumps all around it that look like knuckles. It is not the 351 Windsor or 302 unit. they are different (taller and smoother).
It was removed from an original 1970 Mach1 by me several years ago.
It has the plastic elbow and the Motorcraft part name on it. No damage to the part. Never repainted. It needs a coat of black paint to look new again. no rust just clean it up, paint it and voila!
Make me an offer.
Thanks