I think you need to decide (or if you have already, then tell us) what your trying to achieve from the rebuild?
I wouldnt waste my money on performance parts for a 2.8, its far too easy to simply drop in a forced induction motor or a v8, and i'd bet you could buy an S4 engine or a V8 and install it for less than it would cost you to freshen up your 2.8.