NA gearbox are weaker and have a smaller clutch, depends what power you want. If your thinking about just using a donor NA because of your budget a corolla 1.3 will do as well, you might be better finding a 6speed Corolla G6 just for the wow factor. Or find a yaris tsport gearbox as they have 4.312 final drive you'll still need a Starlet bellhousing but you could always be the first person to do it. I've actually got all the parts but can't be arsed being unique. Tops out @ about 140 mph with the Glanza rev limit coupled with an LSD (also got) would be a quick quarter mile.