You don't need the engine harness, you don't need the ECU. You need the clutch pedal assembly, clutch master cylinder, and clutch lines. You also need the 5-speed brake pedal. Then you need the shifter assembly, boot, knob, and cables. Of course you need the tranny, clutch kit, and don't forget a flywheel. When you get the tranny, make sure the slave cylinder is still attached.
You can use the 6 speed with LSD from a 4AGE 20v blacktop. They are hard to find, but if you head over to
www.club4ag.com you can sometimes find one from someone that is putting the engine into an AE86 (since they can't use the tranny).
-Doc