it can be done although the 4WD conversion would be expensive and require a lot of custom fabrication. you could do it just as a FWD conversion and getting hold of an engine, gearbox, ecu and drive shafts would be reasonably easy. the engine you need from a celica GT4 along with the ecu and wiring (st-205 model would be best as it will easily and reliably make 300bhp with very minimal mods) and the transmission side is MR2 turbo (some easy mods needed to the gearbox for FWD and the outer CV joints need swapping for GT4 items) the only real headache you will have is the wiring. while its easy to get the engine running your cars stock ecu controls a lot more, like alternator, power steering, dashboard etc and as such need to stay but be fed with the right signals from the 3S-GTE ecu. adrian at fensport may be able to help you more with the details as he has done this conversion best place for parts is the good old internet, look for people breaking cars etc but as to see the car running before you buy. trevor at TCB (toyota celica breakers) is another good lead.