Weight of 7 1/4 vs 8 1/4 vs 8 3/4 vs Dana 60?

You can generalize the weight of the various rearends, but "what does x rearend weigh" cant be answered. It depends entirely on equipment and width and application.
A full width c-body 8 3/4 with 11"drums will weigh more than a passenger dana (as opposed to a truck dana) with discs and a spool at a-body width. Even a narrowed truck dana with thick axle tubes and 35 spline axles and 11x2 brakes and a clutch suregrip will be a bunch heavier than an a-body 8 3/4 peg legger with 10x1 3/4 brakes.
The above mentioned test where the nine inch ford was heavier than the dana was entirely due to the very heavy ford brakes. Without the brakes, the dana was about 25 lbs heavier (i dont
remember exactly, been a long time since i saw that test.)
Of the generally used performance rearends (my personal opinion ONLY!) the 12 bolt, 8.8 ford, 8 3/4, and 9" all weigh pretty much the same, if equipped similarly, and a dana 25-50 lbs more, depending on equipment.
I think the 8 1/4 is lighter, and the 7 1/4 dont weigh much at all.