What Clutch with 6-Speed Transmission?
 

I got a 6-speed transmission and going to install it on my turbo 91 miata. Was wondering if it requires/suggested to replace the clutch and flywheel with a 1.8, or leave my current clutch? Any thoughts?

Use the same clutch as if it were a 5-speed.
You can use the 1.6 size if you want or the 1.8 size. I say if you haven't had problems with your current clutch, then don't spend the money on a new one.