Tyler, your "dash-1 ZF", if its in a Pantera, is in fact a Mangusta transmission rotated 180 degrees & attached to a sand-cast differential housing, with the ring gear swapped to the other side. The transition bellhousing has two small cooling holes up on top and only 4 bolts. The first 500-or so '71 Panteras got these transition ZF assemblies that Lloyd Butfoy of RBT Transmissions calls a 'dash-1.5' ZF. They were used while ZF got their assembly line up & running for DeTomaso/Ford. A true dash-1 ZF only fits a Mangusta or GT-40, has a different access cover facing up and the shifter assembly on the lower right.
There's nothing intrinsically wrong with that unit - it was used in pro racing in the '60s & '70s- except that spare parts for them are virtually nonexistent and quite a few things inside do not cross to the 5DS-25/2 ZF used in most other Panteras: mainshaft, synchro assemblies, gears, differential etc. Contact Lloyd Butfoy at www.RBTTransmissions.com
and see if the gearing you think you need even exists anymore. I advise not spending much effort/money on that early ZF and buy a later dash-2 assembly to play with; at least the very high-priced spare gears will be available from Lloyd. You are working with a rare museum piece. Even the GT-40 guys use dash-2 ZFs these days.