Joe, I'll do my best to convince you that Mazda Comp 1.6 (6 inch ring gear) limited slip (NOT the viscus limited slip) does/did exist. From memory the first item one could no longer purchase from Mazda was the limited slip housing with the internal guts. The second item one could no longer purchase from Mazda was the limited slip internal guts. There should be Mazda Comp limited slip differentials out there. Why, because MANY folks who race 1.6 Spec Miata converted to the Miata 1995 plus torsen differential with a 7 inch ring gear.
Included are two videos which one shows and one talks about the Mazda Comp 1.6 limited slip differential with the second video showing the Mazda Comp limited slip at approx. 4 min. 34 seconds.
Video by long time racer Mark Bennett.
https://www.youtube.com/watch?v=mZWFB9D7WQoVideo by long time Differential builder.
https://www.youtube.com/watch?v=qlmkmrDbLPIMaybe along the way Jesse Prather or someone else with knowledge will notice and confirm.