ecu, fuel and brake lines, brakes, rack and pinion, suspension, rearend, transmission, transmission crossmember, brake booster and master cylinder. if not already, you'll need the v8 engine harness and if you have to go out and get it, i'd get that as well as the matching dash harness from the same car. makes it easier when installing it all, including v8 gauge cluster. also, when i did a 4cyl conversion, the way i switched over all the front braking and suspension stuff was i disconnected it all as one piece. disconnect the strut at the strut tower and disconnect the a-arm. that way, all the brakes, balljoints, a-arm, etc. is still all together so all you have to do is move the whole setup over to the 4cyl car and bolt it back up.
actually, you can use that 4 banger transmission if you want to.