IHI do not have very good reliability reports. Quite a few blown turbos.
Getting power down is not a really big issue - get an LSD and drive it properly. A bit of spin in the wet maybe.
For sefety, get internals done if taking torque over 300. There are reports of the standard internlas coping but if you are spending that £££ not much point risking it. For what its worth, when mine was converted (before I got it), it did run 350ft/lbs on standard internals for a few thousand miles.