Good idea about engine and box, only thing is use old engine mounts that
you dont mind breaking whilst wheeling and shifting the engine on the
subframe (trust me it will bend twist them a lot), once its all in place
lift engine (on a hoist) and replace with good new mounts.
You will need to lift the car a hell of a lot in order to get it all under
the front panel, make sure you have the height in the garage. Its possibly
best that this method is used in a wide garage so one can get down sides
of car and stuff, secondly one is not in a rush.
I would say you need at least 3 foot raise as the front in order to get
the engine in.
see picture for a car I did this way years ago:
http://www.annteak.com/images/HCs/Sienn ... CN2311.JPG