I'm pretty sure the 3.3 steering and 2.5 steering is the same... They came out with an upgrade for the e-maxx though that is a lot like the pro-line steering upgrade.
Not sure if it's usable or not in the t-maxx though:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXTKN2&P=7
Tower hints towards that it is usable on the t-maxx if you read the REQUIRES and COMMENTS.
Or, you can just save the hassle and get the pro-line kit:
http://www.rcplanet.com/Proline_Performance_Steering_Kit_p/pro601900.htm
I had that many years ago and it was far better than the stock setup. You will need to get a new solid servo horn if you intend on using either of the above though. You don't use the saver that is on the servo directly with these. It's built into the assembly.