FWIW- as far as I know, the ZF serial # is 'of interest' but is not sequential nor mentioned anywhere in the original sales or shipping papers, and isn't on any of the various tags rivited to the body. There are actually TWO different numbers- one stamped on the top of the rear tranny case and the other on the riveted ZF tag. The numbers do not match in the two locations. In addition, most of the 150 or so early '71 type 1-1/2 ZFs (Lloyd Butfoy's authoritative description of these transition ZFs) used in pushbuttons were changed out by Ford-USA free. These ZFs used a Pantera diff case combined with a Mangusta transmission and gearing. The low-geared boxes with a 351-C encouraged over-revving even with the OEM hydraulic lifters and cam. Its' 4.50:1 ring & pinion gave shattering acceleration but only about 135 mph top end @ 5900 rpm (valve float) in 5th. Combined with the small unbaffled oil pans used, the results were engine warranty problems for Ford, who then replaced and scrapped every early ZF they could find- even in gray-market cars privately imported from Europe. There are stories of large mounds of these early ZFs waiting for the scrap-metal trucks to come haul them away. The few that are left have virtually no spare parts available, as many internal pieces were Mangusta-specific or modifications to that ZF, properly termed a 'type 1'. Ford ordered one spare ZF type-2 for every 10 cars sold, and later found the ZF to be the strongest, most dependable part of the Pantera. All the factory replacement ZFs had no stamped number. An unknown number have been used in Panteras and many kit cars, and they still turn up occasionally for sale.
Bottom line: the ZF 'serial' is not part of a 'numbers-matching' Pantera.