S,

A machenic with craftsmenship and good sence of what he is doing will be able to do the job.
A mate of mine fitted an '2000 Nissan engine on an old '1980 Landcruiser Gearbox 4 speed and it works fine for up a year now.
The only big obsticle is making a centre peace to link the two parts together.

Also mind you the 2.8 Rocky engine is longer so you will have to create space in the engine bay and you will need the bigger radiator from the diesel because cooling is crucial.

Also the engine is hevier so you will have to enforce the suspention.
Better yet switch to the Rocky mine is like a dream come true...

Goodluck,

Gilly