"t3 and t4 are only the exhuast housing bolt pattern. There are 1000's of each turbo."
T04B , T04E
This information is off the Turbonetics web site
The T3/T4 Hybrid turbochargers consist of a T3 turbine section, (F1-49, F1-54, F1-57, F1-62) and a T4 compressor section (T04B trim, T04E trim & 60-Series). This combination offers the low inertia and fast boost response of the lightweight T3 turbine wheel and the high-airflow characteristics of the T4 compressor family.
Did I mis-understand what you were saying about it not being an available Turbocharger.