if you have all the bits you need from a fiesta then all you need to change is the engine,ecu,map sensor,and obviously the turbo ( but id go for a T3 from an escort turbo) everything is there in the orion ready for you! advice on the the turbo tho,see if you can get hold of a turbo like a hybrid that has a 48 exhaust housing as you then wont have to make an elbow shape pipe,and all you have to do is put an escort turbo system on and then just get a longer backbox! good luck with the conversion!!! let me know how you get on.