Push, that's a nice looking tank. The OP didn't specify what year his Pantera was. Note that on pushbuttons, the upper part of stock gas tanks were different shapes than in '71-up production Panteras. For instance, Ted Mitchell found that the stock alloy tank from his '71 pushbutton would not fit in his '74 since the upper left chassis subframes were different. The right side subframe was not checked but was likely different as well. To make the early tank fit the later car, Ted had to cut the whole upper section off, modify it to fit, then reweld the parts. Quite a bit of work for a 6 lb weight loss with about the same 21 gal fuel volume. This was subject of a POCA Newsletter article in April 2011.
The early and later Illustrated Parts Manuals shows different part numbers for the various formed steel beams that make up the rear frames, for different years. The long tank retaining strap was also a different length. So your dimensions may be of limited value to most other owners.