Just wondering, is there any difference between the au1 au2 au3 and te50 snorkels?? like length, throat size appearence etc

Guess it depends what model AU 1, 2 or 3. I.e an AU3 Forte uses a smaller snorkel than the XR8.
Basically the biggest snorkel is the Tickford one (there's only 2 for the AU range, the standard one and the Tickford one) - it's the one used on the Tickford V8's, it's got the Twing logo on it too.