There are three possible positions for the engine, which is dictated by the gearbox type, bell housing used and the position of the transfer box.
Virtually all R380's had the long bell housing irrespective of whether it was in a Discovery or Defender, the exception is the short (stumpy) bell housing used when they were fitted behind 2.5 N/A diesels in military 90/110.
If it has a short bell housing the engine will be right up against the bulkhead at the rear of the engine bay. It should have the big engine cross member and everything should be the same as an LT77 installation..
If it has a long bell housing the engine will be right up close to the radiator. In this fitment the transfer box should be two inches further forward than a LT77 installation, which also requires a R380 transmission tunnel, seat box and props. This installation should use the cross member shown in my post above and doesn't have the big engine cross member.
If they have used the long bell housing and fitted the transfer box in the LT77 position then the engine will be in a different position to any standard Land Rover fitment. A R380 gearbox cross member won't fit and you would be better with an engine cross member of some description.
It depends on what parts are going to foul on the cross member, but I imagine it is the exhaust. The thinnest cross member is the one from the TD5 and later, which will miss most things, but modifying an older cross member may be cheaper.