Just purchased this rear end. It's from a 1990 3.0 DLX manual. They are telling me it's a 6cyl rear end but does not look like pictures I have researched.
^what he said. Only the 2wd 4cyl trucks got a 7.5 starting in like 1979. 4x4 used 7.5 for the front diff for all years I think.
That is an 8" rear end so yes it's V6. 2wd V6 use a 2 spider differential while the 4wd V6 use a 4 spider differential and a heavier cast 3rd. They are fully interchangeable with each other. 7.5 is used in the front of IFS 4wd never solid axle.
I've ran both 4 cylinder and V6 3rd members in the stock 8" housing in my autocross truck. Prior to that I've ran both styles and High Pinion in 4x4 8" housings.