As far as fitting a 4wd gearbox into a 2wd car, not an issue, i mean look at those evo converted protons, its just a matter of fabricating a blanking plate.

before committing to the project (from the looks of it, pretty sure u are already decided) make sure the B8 would mount up properly and legally and how much work is needed.
This is certainly not an impossible project, there are 323's in malaysia with the conversion, i am just not sure what kind of effort has to be put into building one of if one needs to grease any hands doing so. If you can find other owners who have done this, that would be the absolute best. Its these guys who have converted these cars who would know best.

*edit... looked at some stuff and actually, it looks very straight forward. car was readily available with a bp (basically b8) so the bpt should just bolt in. (really not difficult if yours is already running the 1.8 bp)