Which Rear End Is This?

Thought since I have a 318 from the mid to late 70's that the differential would be the standard 7 1/4 but this looks more like 8 1/4 but the cover seems that it is something else... I came across a picture of a Ford 7.5 differential so now wondering if someone before swapped in a Ford rear but I don't know.



[ame]http://youtu.be/shMcJDBkcyA[/ame]