The 4A-GZE represents Toyota's first ever attempt at designing a supercharged engine. The supercharger design is roots type which is cooled/lubricated with its own special supercharger oil.  The boosted air is cooled by an Nippon Denso air-to-air intercooler mounted right underneath the engine cover's (unique to the SC) cooling vent. When the 4A-GZE was introduced, Toyota added significant strengthening to the block so that it would be able to handle the rigors of forced induction. It has extra ribs and a great deal more metal all over the block.  In addition to this stronger block the 4A-GZE had 2 extra things added to it to make it different from the 87+ 4A-GE engines, that being Forged Pistons and Oil Jets to cool them.  Surprisingly the camshafts from the 4A-GE are used, but they work quite well. 

The US version of the 4A-GZE which was used in the AW11 was also used in the AE92 in the rest of the world. In late 89 an improved version of the 4A-GZE was introduced in the non-US Corolla/Levin. This engine produced 160 HP as a result from higher compression ratio (8.9 vs. 8), and the switch to a MAP air sensor. The engine was also improved upon slightly in 91 and HP increased by 5. As you might of guessed, these Japanese spec engines are sought after by AW11 owners to be transplanted into their MR2. There are many available modifications specifically for the 4A-GZE, from larger crank pulleys (for more boost) to larger intercoolers.

For info on how to get a 4A-GZE into your NA car go to Steve B's SC swap page

David Kucharczyk has provided the following excellent write up of the SC engine:

Notes for the SC from the 4A-GZE