most of them actually weren't posi... seems that most cars ordered by the dealers just got ordered with a "package" of options, and since limited slip wasn't in there, it got overlooked. From what we have seen, we'd take a guess at less than 30% of them got the G80...
FYI,
I picked up a 3.73 8.5 axle from a H/O or 442 from a junkyard. It was 3.73 open as well. If a car has more than 30K miles, the posi is usually worn out anyway, no matter how they look.
Hell my 86 GN was open diff with 3.42 gears. It has the G87 but no G80 on the built tag. It is now though. That has always been a s/o option. On almost everything. You are right about them always being toast though. You are usually better off purchasing on open rear end like this one here and putting a new posi in it... if that's what you want.You will save money in the long run. Good price BTW!!!