Here's what Bass Junky emailed to me one day.
I sent him the pic and he sent it back.
"Hi,
Looking at the photo, I will make an assumption that the top turbo is of an R34 GTT.
I have added a couple of little lines on the photo which illustrate the differences that I think there are between the R33 and R34 turbos.
The relationship between the width of the gap between the snail and the flange, and the width of the flange itself is a pretty good indication of the turbo.
R33 has a wider gap than the width of the flange, and the R34 or VG30 turbo has a gap which is slightly thinner that the width of the flange.
Does this make sense?
Cheers"