[WKB]

Merv,
The R32 is 4.3:1 and from all the information I have the R33 is the same. If yours is a R32 the S13 Nissan Silvia diff(3.7:1) will fit and only need the drive shafts from your diff fitted to the new diff and will bolt straight in from the bottom, a reasonably easy job. The manual S14(viscous lsd) and the S15 (gear lsd) will fit in with some mods. The spline for the drive shaft on the S14 and S15 are different so an adaptor has to fitted between the drive shaft and axle. If it is a R33 the S14 and S15 diffs might be an easier option.
The back cover from your diff also needs to fitted on to the new diff.
I bought a S15 diff from Ebay. There are a couple on ebay right now and they both are from a seller on the northside of Brisbane.

Warren