Its the big unknown so you wont get answer..

Its going to be a try it out and see.

I reckon the 6speed box or perhaps a mtx focus rs box which is in MINT condition iternally would handle that power, for how long who knows.

Theres people who have run 500hp through a stage 2+ box which lasts a while key to it all is having a good strong well built box.

Unles your building this as a pure drag strip/topspeed car 600-700 hp is wasted for anything else. Id budget a good 25k+ to achieve that kind of figure.

If your wanting to go 4x4 route then thats a differnt matter, evo rs running gear is the way to do it but again thats going to cost you bet part of around 5k in transmission.