I don't have direct experience with the 1973 Challnger to know for certain. But...
Since AMD sells a single sheet metal panel, for all Dodge Challenger years 1970-1974, I'm concluding the sheet metal is functionally and perhaps visually the same.
This means the two-piece 1970 trim, that goes inside or on this panel, will also fit and be functional on any Challenger year 1970-1974. Even if it's not model year correct for a given car. If an owner likes the trim, it should bolt in to place.
Any missing holes will have to be added. This is because when there IS a variation in the sheet metal, AMD only wants to stock one variation, so the leave off elements that can be added. For example, buying a shaker hood from AMD, it may come without the holes for the hood pins, because hood pins were an option.