More information to answer some of the questions (hopefully) :

The gearbox was built up with all new gears and bearings/seals etc. but retaining the original shafts and gearcase.

It has an uprated viscous coupling fitted as well.

It does retain the standard ratios for Group N homologated use (where they had to be retained).

The gears are all helical, there are no straight cut ones.

The Quaife gears are huge compared to the standard ones, at least 50% bigger.

The box has only done about 50 miles from new.