What you show in your photograph is a speedo cable drive, onto which a 90 degree adapter would normally thread. Two types were used VDO or Veglia Borletti, one has a flat drive the other a square drive, so if looking for a cable to match be sure to get the correct matching one.
Close, but not quite.
Take a look at this diagram from the Panteras by Wilkinson website:
ZF Gearbox Parts
Specifically, look at the parts #801-806; that's the speedometer drive gear and associated bits and pieces. The 90-degree drive is the unnumbered part which appears above it (and is formally listed on a separate page,
here)
The piece in the photograph is actually a straight variation of the 90-degree angle drive; it's ready to have a speedometer cable attached directly to it. It's interesting; I've never seen one like that before, although I admit I haven't paid close attention to that detail on GT40 gearboxes. Could it be an original GT40 part?
The GT40 parts book shows the straight output gear etc. (also numbered #801-etc.) but nowhere does it show the adapter or the cable. So perhaps that's what you have?
To install an oil pump (cooler) you will need to have ports drilled into the ZF, there are apparently cast boss locations to do this, although I'm not sure of their specific locations.
In a GT40 application, one line is installed on the right side of the shifter mechanism case, above the shifter. It uses the threaded hole that is normally used for the oil filler plug in Pantera applications. The return line comes from a threaded hole which appears on the bottom of the shifter case, and was the drain plug for GT40s that weren't equipped with a cooler setup.
Early Pantera gearboxes (Dash-1s and early Dash-2s) have a seemingly useless hole here with a plug (on the top of the gearbox in Pantera orientation); those are there because ZF was using leftover pieces for their manufacture. Starting early in 1972, as the supply of leftover parts from the GT40/Mangusta/etc. production ran out and gearboxes were being built specifically for the Pantera, that boss was left undrilled. It's critical that this piece be drilled and tapped for a drain plug when a later Pantera gearbox is flipped over to be used in a GT40, otherwise there's no way to get the oil out!