FYI, while there are obvious weight differences, the Dana 60 is more "efficient" than an 8 3/4 rear. I've been told by several class racers that in most cases, there has been minimal, if any, change in ET. The Ford 9" is probably the least efficient of the popular rears and the Chevy 12 bolt is the best!

It's been discussed and, for some reason, 30 - 40 lbs sticks in my mind. But it will have to be an apples-to-apples comparison with the same width, spool or sure-grip, etc.