5k turbo motor in a 4k

[Marc Swanson <marc@lodoss.mv.com>]

        ok, I checked the archives and couldn't find to much information on
this topic.  A friend of mine is into scca pro rally and is running a
basically (I stress basically) stock 84 4kq.  He has a 5k turbo motor from a
junked car that has a brand new turbo as a donor motor.
        My question is has anyone done this?  And if so, what kind of
general problems did you run into and anything special to look out for.  If
this is in the archives and I just missed it, I appologize.
        TIA
                                                -Marc-