It's an adaptor plate for the 1hz engine (4,2D NA) but for what gearbox I could not say. I would assume its for the 4.2TD gearbox but I could be wrong.
An adaptor plate is used when bolting a gearbox to an engine block that it was not designed to work with, an example would be ford 3lt V6 engine and lame rover gearbox (done a few of those).
Have also fitted a ford 3.2 V6 (modified 3lt) to a porsche 922 transaxle gearbox and fitted to VW Microbus, that was a fun car, and done a chev 350 V8 on to a dyna 4 ton truck gearbox into a 40 series pick up, even more fun.
but the best one I ever worked on was a merc 2624 where we fitted a gearbox and diffs from a merc 3336, that was a fun truck, before conversion it had a top speed of 90 kmh and after it could almost hit 160 kmh on the speedo (calibrated for tacho) and all on standard truck suspension and drum brakes
oops, thats me off on a tangent, ......