Adding weight to the rear end helps, but that still leaves an open diff. with one-wheel-drive.

"G80" is simply GM's RPO (Regular Production Option) code that specifies the vehicle was originally equipped with a "locking differential", whatever that may be at the time of production. It could mean limited slip on earlier models, or a locker on later models.

My understanding of Eaton's Mlocker is, it's similar to (or the same) as is offered on OEM GM vehicles since 1995, but an aftermarket label offering. It's a good system, but engagement can be a bit harsh. It requires a wheel speed differential of about 100 RPM's (which isn't all that much) before it engages, and when it does, it's a positive lock, and doesn't unlock until all differential loading is relieved for a bit of time and distance traveled. I've had several trucks with it and it works very well, but like I said, engagement can be harsh if traction on one wheel is very good, when the slipping wheel locks in. On a positive note, this locker doesn't require any additional maintenance or additives, compared to a limited slip option which requires more frequent service, and a friction modifier additive for proper clutch operation.

Still, in my experience and opinion, for most all 2WD applications, limited slip is the better performance option.