Bune,
The Pantera gearbox is a ZF 5DS25-2.
Ford GT40 MK3s were the "Street" version of the GT40s and the only ones that used ZF boxes. These transaxles were used in ther MK3s because the are sychromesh (use hylically cut gears) and cannot handle the power demands of LeMans racing. I believe there were only 9 GT40 MK3s manufactured by Hollman & Moody in the late 1960s.
The MK3's used the ZF 5DS25-1 transaxle. The primary difference between the Pantera and the MK3 gearboxes is the mounting configuration. The ZF 5DS25-2 is rotated 180 degrees about the center axis when compared to the ZF 5DS25-1. Also the mounting points differ.
I was very fortunate to buy a used ZF 5DS25-1 from Hollman & Moody in 1972 (for $500) when they got out of the GT40 business. I mated it to a small block Chevy V8. Similar to the configuration used in Lola T70.
I later picked up a spare ZF 5DS25 (no dash number). I assume this version preceeded the ZF 5DS25-1. These two gear boxes have similar mounting confgurations, however the driveshaft on the 5DS25-1 is much shorted that it's predecessor. The second transaxle cost ~$1,000 in 1982.
If the price doubles every ten years, that would put these gearboxes at a current market value of ~$6,000 to $7,000.
$3,000 in today's market sounds like a great price for a ZF transaxle.
Good luck with your pursuit! I hope you can locate and buy one of these.
Dr. Mike