You could go either gsr tranny or si tranny to upgrade. They are both stronger then the ls tranny, gsr the strongest of 2. The downside is that they both are shorter in gears and get less gas mileage. Also you wouldnt get much of high end power with the ls motor cuz its low power and good amount of torque. If ur going to do a lot of highway driving then stick with ls tranny. If not, well you can have fun with gsr or si tranny.