There is an alternative to the z33 cover is the R51 cover. Its a 2 bolt which IIRC is about an inch more narrow then the s14 spacing. I started modifying a S13 subframe, got the diff in place but, never got around to finishing it. Mainly cause I haven't had a chance to get a better R&P set then the R51 2.3. Ratios go from 2.3 in the R51 all the way to 4.6 in newer 2.5 frontiers. It also comes with a axle output flanges that are bigger then the Z/G but they swap over.
There's an issue with the conversion bushings that most people done see. It lowers the differential placement in the car ~3/4 inch. This not only increases the drive shaft u joint angles accelerating wear but, increases the driveshaft angles weakening the their joints especially on a lowered car.
