David, I sit corrected, but not OEM, just Mazda Comp. I just looked in a 1997 Mazda Comp catalog. It shows:
Part # T0Y1-27-200
Description: Mechanical L/S
Model/Engine Type: Miata 1.6 1990-93, 323 GTX 1988-89
Notes: Easy bolt-in fitment to non-viscous limited slip
Miatas. Replacement of viscous-type
differential requires changing output shafts
(Part #T005-27-270B).
I raced on an enduro team in a 1.6 spec Miata with a viscous LSD. The car had gone about 25,000 track miles before that LSD blew up. They can work. We should have better monitored the pinion play. The crush spacer likely crushed down over time allowing the pinion to float around. 8 hours into a 24 hour race it decided that it had enough. We had a spare center section, but when it blew up it took out the aluminum housing and that finished us. I'm not so sure that a clutch type would have held up for that many miles.