I've been replacing the motor in my '95 Disco recently. Well, I've been paying some mechanics to do it for me...
As far as I can tell, if they are both the 3.9L motors, the parts should swap. The concern is with the onboard computers, many of which won't work properly if you do swap the parts. I'm not certain about the computer hookups for the fuel pump, but that is one thing you should look into.
For these sorts of things I've had good results calling the mechanics at the Rover Dealer closest to me (Portland, Ore). They are usually quite good about answering questions, and as long as I'm very clear and specific, they give me good information on what is "Rover authorized" and what "isn't official, but this is how it works..." Not being much of a mechanic myself, they have sometimes left out details that I would have preferred to hear about, but not anything that's been a major problem.
I've also made some contacts with local Rover clubs and other Rover owners. They have also been helpful in getting me going in the right directions.
Hope this helps.
Alex