Engine replacement and compatibility

[marcodelhierro]

Hello, I am new here and need help.
I live in spain and have a mk4 transit with 4DA engine.
The problem is the car did not pass the emission control (almost 9/m opacity). It consumes a lot of oil, I suppose because of worn pistons/rings so i´m thinking it might be necessary (and less expensive and less complicated, i suppose) to replace the whole engine.
Now, i dont know whether the engine you fit in should be exactly the same, ie 4DA, or it does not really matter?
Can I use in mk5 engine as well?
Where can be found more info on engine replacement?
I´d appreciate any comment or opinion.
Thanx.

[MinorMatt]

Any onld engine will do - so long as its the same type ie. 2.5 diesel