They have T28's with ceramic turbine wheels.
The one I have, that was allegedly off a skyline, has a steel turbine and aluminium compressor wheel. But, there is nothing to say it hasn't been swapped from ceramic at some point.
Opinions vary on the ceramic turbines, some say they are pressure limited and fall apart if you run too much drive pressure (which correlates to too much boost pressure), others think overspeed kills them and others think excessive EGT kills them and with safe EGT's you can run 30psi boost with no problems.
I couldn't run mine as a single turbo because the exhaust housing mounts with threaded bolt holes and my manifold does too. So I stripped that T28 and built it up with a T25 turbine and exhaust housing. I also used a T25 compressor cover which I bored out to fit the T28 compressor wheel.
This is the DIY T2560 that I run.
The Isuzu 4HE1 turbo has this same 60mm T28 compressor fitted and only requires a simple adapter plate to fit to the T3 manifold. It is my current recommendation for a close to bolt-on Garret turbo which has enough capacity to wind out a 4BD1T.