As near as I can tell, but double check this. You have a GM 10.5 inch 12 or 14 bolt rear end. Used from 1973 to 1984 and beyond in some cases. Truck axle used in lots of applications. Too much dirt to get a good count on the cover bolts.
This might be helpful: http://www.nationwideparts.com/differentials.htm
Good luck.

Steve H