Send your ATX tranny to Level Ten. Then, put it back in and revel in the fact you have a VERY effecient ATX that can handle gobs of power/torgue generated by the turbo'ed Zetec.
Why make things harder? Save your time, money, and headaches.
Well over 300HP/TQ utilized safely by a very strong Level Ten ATX tranny. This allows you to keep both hands on the wheel. :p