WestonXR3i

I've just bought a mk5 xr3i. I wanna keep the body as original as I can but i wana put a beast under the bonnet instead of the 1.8 105 it comes with. Also wana convert the rear brake drums to discs. Im thinking of dropping in the focus st170 engine and gearbox with complete drivetrain. Can anyone advise on this fitting etc. Was also going to use the brakes from the 170 for the front. Im fairly sure these will fit with a bit of tinkering and bracket drilling. Cant find anything on the rears though, will the st170 hubs bolt on direct, If so then the entire 170 braking system it is. I've done a bit of homework but cant find a definate answer for the rear breaks etc. just wanna see if anyone has other ideas!