You could buy a AE82 twincam with all the work done but you might have spent alot of your SOHC model so you might not want to get rid of it or whatever.
Anyway you will need a complete 4AGE engine, Gearbox, Engine loom with all sensors, Cabin loom, EFI fuel tank, Oil cooler system, Drive shafts etc. Your putting a twincam in a ae82 SOHC which has shit brakes so you might as well take the brakes from a twincam as well.
If you really want to keep your ae82 buy a twincam and transfer as much of it over as possible.