The original drive shaft in my '86 NA went bad the other day. I replaced it with the Mazdatrix shaft that comes with replacable u joints. The cost was around $240.00 versus over $300 for the Mazda version.

I am amazed at how much better this drive shaft is than the original. The car is much much smoother, with zero vibration in the drive train now.

I can highly recommend this as a replacement.