Guys is a .48 housing the standard one to use on my 1988 Sapphire?.

I say this as I'm about to buy a T34, I know you can get .63 and possibly a few other sizes but I know sh!t all about turbos and how the housing size affects the fit/performance?.
I've ben told by both my Cosworth mechanic and Simon at Woodford Garage Motorsport that a .48 housing is the one to use.
I just thought I'd check here with you guys before I forked out the money for one.

The reason for the confusion is I live over here in New Zealand and the distributor over here seems to think that there is no such thing as a .48 and is telling me that I need a .63 or something along those lines.

Cheers again