You can use the n/a clutch or the turbo clutch but to use the turbo clutch you will also need the fly wheel as the turbo clutch has a bigger pressure plate and disc.
I dont think the turbo box is much stronger I have run over 250hp on a N/a box with no problems but the turbo box does have a higher ratio 5th gear to the N/A box so its better on the motor way I think.