I don't have G80 or G86 (unless I missed it) listed in my glove-box but I'm pretty damn sure I have some sort of LSD.
Here's the results I get when I look up RPO code G80
"G80 Differential, heavy-duty locking rear
G80 Differential, automatic locking rear
G80 Differential, heavy-duty automatic locking rear
G80 Differential, limited slip rear
G80 Differential, limited slip
G80 Differential, locking, heavy-duty, rear
G80 Differential, Zexel-torsen, limited-slip, rear
G80 Differential, automatic
G80 Rear Axle: Positraction
G80 Locking, Rear Axle
G80 Axle Positraction Limited Slip
G80 Differential, locking, rear
G80 AXLE POSITRACTION LIMITED SLIP"
I think it might depend on the year and application, unless GM just tossed both terms around to mean the same thing.