I think you'd be dumb to change engine from non turbs to turbo. I'm pretty sure there is more than a brake upgrade as well, things like suspension would have different spring rates and the dampers would be different as well. As a turbo engine would weigh more than an NA.
Like people have said 34 GT-t has a stronger box than standard GT, diff is different, tailshaft as well, etc, etc.
What happened to the supercharging idea?