Did the remanufacture the guts of your 6r80 with anything special?
Hardened and treated gears?
Better clutch bands?

I have heard of modders using a stick 6r80 with over 700 HP at the wheels, but 1000 HP is just plain sick crazy powerful

 

better clutches, he machines the drums to accept about 40% more clutch material,

also makes a few proprietary modifications as well, mainly for lubrication and a better support bearing