Mark post a pic of the diff up...

Ive only ever had the ford grp'a' stuff so I cant tell you really about the R & D, but if you were fitting a grp 'a' 7.5" diff, you would need the correct sump and cross shaft for it all to marry up, at each side (diff and sump) you would then have ouput flanges to accept the inner lobro's (100mm on ours) if you were using standard uprights you would have to get one off drive shafts to convert to standard out cv joints....I have been involved in car with this set-up and we had some shaft made by Dennis @ Dome.

Grp'a' 7.5" sump are I think approx £1K cross shafts approx £500....WRC sump for the 8.5" are 2.5K cross shafts £1k s/h....

grp'a' shafts are not splined the same as a standard shaft

HTH

Ian