There is the Universal Turbo's T38 that is based on a T34 frame with machined housings etc, meant to be good for approx 440ish with almost T34 spool-up

then there is the Turbo Technics T38 that is a T4 frame but slightly smaller housing a/r's and wheels etc. Meant to be good for 470ish approx with bit better than T4 spool-up.

Unless you want to push a genuine 400BHP +, and have the headwork to cope with it then stick to a T34.48