A T3 is a T3, on a std cossie 2wd this would be a T3.48(exhaust turbine), then there is the T34, which is exactly the same as a T35, all three T3/T34/T35 can be had with .48/.55/.63 exhaust housing, a T34 and a T4 are 100% different, the T4 is a monster by comparison to a T34.
To further confuse things, you can get, as I have a T3.48, with the standard T3 compressor housing machined out and uses a T34/35 inducer(compressor wheel).
The escos T34 had a cast in actuator mount, but can also be used with a T3 actuator mount instead, the reason is fitment when the two housings are moved in relation to each other to make things fit, this can put the alloy cast mount in the wrong place.
tabetha