the only this i have been told is that the 5m is easier to wire. but idk. to be honest i dont even know the difference between the 5m and the 7m i just want more power for the celica thats all. if the 5m came in the celica supras then it should be reall east to wire up. i would probably just have to pull a harness from one of thoses cars and switch it over but i cant really find the info on what engines came in those cars...its a big fuckin headache! lol