The tremec is a little bit beefier than the T5, so I would imagine some massaging will be needed to get it to clear. It would still be worth the hassle though IMO.
The Tremec is wider on top because of the multiple shifter mounting locations. For the T5 I had to slit open the top of the tunnel and add some metal. Easy to do and invisible under the carpet. If the T5 gets damaged from the 347 a Tremec will be my next choice.
Just adding to what everyone else said. With a T5 your going to have to do some massaging of the tunnel and the tremec is a bit wider up top.
I have a Tremec 3550 TKO in my car, and yes the tunnel needs to be enlarged. Not too hard to do, but the crossmember has to be made.