I think that in the near future their will probably be a Rev. 4.5 conversion as I think Speedmerchant is switching over to a 4 bolt rear end for everything.
As far as a CF t-bar, I dont think anyone really runs one, and alot of people I know will even run a 63 t-bar on carpet, and if a 75 is too stiff than i imagine a cf one is way too stiff, also the way it rebounds back is totally different and might make the car a bit screwy on the track.