well it may not be that general but i was wondering if a 4 bolt gt-series t3 turbo flange is the same as a 4 bolt t-series t3 turbo
depends on the housing. If it is for a gt35r then no. it is a 4 bolt almost in a square pattern. There are two 5 bolt standard T3 housings and one 4 bolt that is in the same shape as the standard 5 bolt flanges. A pic of which one you are looking for would help. I could tell you just by looking at it. 
this is the flange that is on the turbo now i dunno if that helps or not
that is the GT style 4 bolt square pattern a 4 bolt from the stadard T3s should not mate up as it is in a diamond like pattern. That is GT specific
also standard t3 style 4 bolt flanges are kinda rare to come by they were used on some borg warner t3 style turbos but that is about all I have seen them used in.
well its actually a t3/t4 turbo but i was just goin by the t3 side where the flange is on