You really need a pan from a 111" WB car. Dart, Scamp, etc, it has a fill panel for the 3" longer wheelbase. They are different from 108" Valiant, Duster, Demon, Dart Sport pans.
The seat belt mount holes changed over the years, about 72 they changed to a position a little further back than 71 down IIRC. You may have to do some small patching to get those holes right if from a different year car,