As for which manufacturer to go with I've got some friends running PAR straight syncro boxes and one with a dox box and they haven't had any issues whatsover in regards to reliability - both have managed to kill nismo mechanical diffs and haven't had any damage the PAR gearsets with the abuse they've been given.
I believe they will only provide warranty on the boxes when they run NEO oil in them aswell which you may want to confirm as it's not exactly cheap in comparison to other oils out there.
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