nobody makes the hydro conversion for d series trannys. your best bet is a 89-91 si tranny. 88 will work, but the splines are different and the clutches made for them are a little smaller because they came with a smaller flywheel, but since your car is an 88, it will be best for you so you dont have to change your flywheel to adapt to a bigger clutch that work in the 89 and 90-91 trannys