I'm doing the opposite, or was. I think I'm just going to rebuild my Disco R380 and keep my D90 R380 as a spare.
You need to change the bell housing, shift linkage, top cover, selector rail and yoke at the end of the rail.
If you have an blown Defender R380 to get the bits from, it is probably cost effective, but if you have to buy all the parts, I'd question the cost effectiveness, depending on what you paid for the Disco R380.
Four wheel drive allows you to get stuck
in places even more inaccessible.
62 88 Regular
67 109 6cyl NADA x2
74 Lightweight - The Antichrist
95 DI 5-speed
95 D90 5-speed
97 D1 Automatic