Ginge
If memory serves me right ... There are 2 long bolts at the rear of the diff + 2 short bolts near the prop flange at the front of the diff .... Finally if it is still in the car, there should be a rubber mounting bracket fixed to the upper rear of the diff ( 2 bolts ) This in turn is mounted to the underside of the cars chassis via 2 more bolts.
If you have removed this lot ..... It'll be just corrosion holding it fast, they can be quite firmly stuck.
It may help if you try to drive a wedge in there to spread the brackets a little. An old large flat bladed screwdriver should do the trick. ( Assuming that you don't have anything more suitable to hand )
