Triple disc was reccommended by the person who built the 4R70W.. Jerry Wroblewski (i think i spelled that right). ASSC is a company that sells all high end racing parts... www.asscracing.com - sponsor tony gillig's pro 5.0 car
specify that you want the triple disc and they have it.
In a n/a vehicle, its not neccessary. Now if you're planning on going boosted or building the vehicle to be just a track car, then yeah, a trippe disc is a good idea. I have a single disc setup in mine and no problems so far.
I got the triple.. for $200-$300 more you might as well go with the triple, it's better than the single and if you ever decide to go boosted, 1. You'll spend $900 all over again to buy the converter, and 2. you'll have to pull the tranny AGAIN to install it. Save up a few more $ and do it right the first time.