It’s from an old square body 4x4.
So it won't fit without cutting/welding.
You'd ideally be looking for a 2WD GMT400 axle. Even a 4WD GMT400 axle is going to be the wrong width.
Your 10-bolt is a piece of crap. I'm somewhat surprised that it hasn't blown-up already. That IS their reputation. They shatter the OEM differential case--open or locker.
Most 10-bolts come with horrible 254mm leading-trailing shoe brakes. That includes the JB5 brake option code you say you have. They're the weakest, smallest rear drums installed on a GMT400. That truck is crying out for a 9.5" axle swap. You need the axle, the larger U-bolt plates, new U-bolts and nuts, and a conversion U-joint. In addition you'd want a rear cover gasket, fresh lube, and whatever axle/brake repairs might be needed.
If snow and ice performance is important, bigass tires are not the way to go.