I understand there are differences between the standard GKN/Salisbury differentials and the short lived Dana44 unit found in some XJS. It is my understanding the ring and pinion are compatible across the different versions.

can anyone confirm this?

 

Probably need to be more specific in what you are trying to do. Broadly, the readily available Dana 44 gearset will fit the Salisbury differential; but there is a ratio cutoff where you would need a different posi unit. The posi units broadly interchange with differences in side gear spline count and ring gear bolt diameter. Ring and pinion sets broadly interchange with differences in pinion spline count and ring gear bolt diameter.
As an example you could put a Dana 44 gearset in a Salisbury unit if you sleeve the ring gear bolts (7/16” vs 1/2”) and use a GM companion flange (due to the different spline count). Then you have to deal with the driveshaft, which may be a different length (due to the flange change). Also bearings may be different dimensions (but are available).
Google will be your friend…..

 

Really just looking for info on factory ring and pinion, specifically ring diameter and pinion spline count, are these the same across the variations of differentials used.

the 16/30 spline output shafts, spacing and bolt holes arent an issue for me.