There are shift kits.
The tranny will work for stock, for a whle. Drive it hard, and band # 2 will wear at a fast rate. There is not a lot of material on the stock band. Do keep it adjusted, and it should help with the life.
I knew going into my build I would need a tranny eventually. I was trying out ROE when they said my stocker would be OK. And they may be right. My tranny problem does not seem to be HP realated. But I am not going to wait till I am on the side of the road, I am upgrading it when the parts arrive next week.
Parts that I am aware we need: Better torque converter (big $), better bands, valve body work for better clamping pressure. For big builds, you start getting into input shafts and the like.