I would recommend D&D Performance in Michigan for the Tremec, or the T-5.
The T-5z is no different from the other T-5's in dimentions or bolting, so your Tri-Ax would bolt right up to it.
I don't know about the Tri Ax for the Tremec, but Steeda makes high quality stuff, I would certainly think their shifter would help the Tremec, but I have heard and seen posts where the Pro 5.0 has helped big time for sure.
http://www.ddperformance.com
That's their website. I've only heard good things about them, and I've had a great experiance with them first hand as well.