I have a 88 hatch with a sohc zc swap with the orignal 1.5L tranny and the factory clutch. As you can guest the clutch does not hold up, it slips like a bastard under power. the thing is that I have a tranny from an 89 si but I do not know what clutch and flywheel to buy and Im not even sure it is from an 89. I need to know how many splines are on the input shaft on a 88, 89, and 90-91 trannys and the flywheel diameter for 88, 89, and 90-91. any input is welcome.

 

88 = 21 splines
89-91 = 20 splines

88 = 190mm
89 = 200mm
90-91 = 212mm

If your tranny has 20 splines you'll need an 89-91 flywheel, then buy the clutch for the same year flywheel. 90-91 is your best bet for the bigger dia, but 89 will work fine.