I believe silvia's are a different width, so they would need slight modifying. I dont know of any skirts that will fit strait on either, so best to get WRX ones and cut them down a little.
Personally i would go for either Silvia or WRX kits and modify... they are so popular that they are cheaper than other makes, they wont need too much modifying, and they would suit the U12 just nicely IMO.
Thinking about it a little more.... Probably your best bet is a kit off a pulsar, they are also made quite alot, and from memory some almost bolt strait up with very minimal mods.