What Rear end is this??

I have the same rear end on a 74 Duster with a 318. The cover looks identical to yours. I had the same trouble trying to I.D. mine by using the chart. Round cover, no drain hole, 10 bolts......but mine had a tag from attatched to it stating it was a 2.71. So I too am glad to know I have an 8 1/4 rear end.