all diffs are basically the same length and use the same propshaft.

the differences are in the width, but there are only 2 different widths. 7 inches from normal sierra's including all 4x4, and 7.5 inches from granada's and scorpios that were also used for cosworth 2WD only.

in the 7" width's, there are differences in the output flanges. some have bolt on driveshafts (all those models with disc brakes), and some don't.

if you can take a picture of your differential and show the driveshafts, i can comment further