I also found that Matt's has the best prices. After speaking with Classic Performance Parts who actually makes the kits, they said that 14's will work as long as it is a factory disc brake wheel (or I'm sure aftermarkets that already fit disc brakes). When I received my kit a couple weeks ago, I fit the front assembly into my 14 inch rally wheel (disc brake style) and it fits just fine. It will be a little while before I get them installed.

I think the reason why many companies state that they only work with 15's is that when they initially started putting front discs not many people opted for this, and therefore there are not as many factory disc 14 inch wheels out there. Most people when looking for wheels don't look for this specific difference and so to cover their behinds, they make this blanket statement.

My $0.02