Yes you can...I used these guys:
http://www.importperformancetrans.com/
Sound Performance does an upgrade on the Auto as well, but are a little more expensive. Stay away from Level 10 like the plague.
This is not something you really want to do yourself, unless you have experience working on autos. I had mine fully built with a 3000 stall torque converter. I also have a TRD LSD w/ 3.90 ratio gear installed...the aluminum driveshaft is ordered and should be here next week. There's not a 5 speed out there that will out-shift me :naughty:.....my car will bark the 275/18 wheels I have on the rear on a boosted shift to 2nd gear.
I want to warn you...this is expensive. The 5 speed conversion is much cheaper. I chose this route because I like auto trannys...I guess I'm lazy. Plus, if you've ever look at dragsters, they're all autos. An auto tranny (if properly built) will keep you in the boost power band and if combined with a shift computer, will allow you to utilize a F1 paddle type shifter. The downside to an auto is it is less efficent at getting power to the ground...you will lose RWHP vs a manual with the same motor. Thats why I upgraded my entire drive train to the rear wheels
I'm not trying to start a manual vs auto flame thread here. I like auto trannys (have since my SS 396 w/ a Turbo 400 days) and will likely not ever change...I just have to up the HP on the motor to compensate :evil5: