All this talk of 8.8s, BW78s and Hilux diffs have caused me to ruminate lately with things that I have discovered over the rears.
As someone who has a number of failed diff upgrades behind him, and a number of successful ones too it is my opinion that unless you are building a very big HP car that you intend to drag race or do mad burnouts with a factory LSD upgrade is all you need, or an aftermarket center. By that I mean adding a Quaife LSD center to your Escort/Anglia/Cortina diff or upgrading the center of your Valiant/Holden/Falcon diff with a rebuilt factory LSD center.
If you are building a serious car with big HP, stump up the cash and buy a 9inch. It might cost you a bit more initially but in the long run it will work out cheaper and better. So to clarify I'm not opposed to 8.8 swaps for example, as said above they are cheap, strong and come stock with an LSD. But. . . factor into that shorten the housing, source another axle, change a crown wheel and pinion, weld on your spring perches and deal with all the worn out bits in a diff that was new 20 plus years ago and hasn't been touched since. Yes you'll have a good strong diff in the back of your car. It will still have C clip axles, bearings that run on the axle, and be a back hat design. In my experience it will cost at a decent percentage so of an equivalent 9inch it will probably cost more than that by the time it's up and running but it wont be a 9inch.
The same applies to BW78 diffs too.
This is my opinion.