What was it SPD (schedule production date) and which factory was it made at?

The Challenger T/A, and AAR 'Cuda, used the 2881489 (aka "489") differential carrier assembly in its 8-3/4 rear axle with the "cone" type Borg Warner Spin Resistant (# 2881343) Sure Grip.

The TA and AAR were well into the run of 1970 so the only suregrip available would have been the cone type and the 489 carrier with the std 3.55 or the options 3.91 ratio. You could still get the 741 small pinion and they were also available with a sure grip. I have personally never taken one of those out of a car to see what suregrip it had.

I wonder if it was a cost cutting measure or something. From what I understand the cone type isn't really rebuildable per se but you can get a shim pack for the cones, Dr Diff has them.
https://www.doctordiff.com/8-3-4-cone-sure-grip-shim-pack.html

I ditched the one in the 489 case in my R/T. The car had a hard life and a lot of miles on it so it was going to get a new unit anyway. I replaced it with the helical gear type, overkill probably but I think they're supposed to be the best.
https://www.doctordiff.com/8-3-4-helical-gear-sure-grip-sure-trac.html

Before any modifications are done, I’d follow the service manual instructions for testing of the unit you have.

I was a little surprised to see this sure grip. I always had the clutch sure grip in my Dana 60
Where to find parts
Thanks

Spoke with Doctor Diff and he has a shim kit if needed. Back in the day it was serviced as a unit. Today some machining may be done.

Thanks

Don't waste your time, or money. To machine the cone type it's going to require complete disassembly and you'll want to change your bearings , ... unless the car only has a few thousand original miles .... the cone type grinds the cones up every time you take a turn, which generates tiny metal particles that float around in the oil and gets run thru the bearings and the gear teeth, high mileage units will have tiny marks in the surface of the bearings and gears from all that metal, they take on a grayish haze from it. It's going to cost almost as much as just buying a clutch type from Dr. Diff and rebuilding the chuck.

The BW cone type is a piece of garbage by design.

Don't waste your time, or money. To machine the cone type it's going to require complete disassembly and you'll want to change your bearings , ... unless the car only has a few thousand original miles .... the cone type grinds the cones up every time you take a turn, which generates tiny metal particles that float around in the oil and gets run thru the bearings and the gear teeth, high mileage units will have tiny marks in the surface of the bearings and gears from all that metal, they take on a grayish haze from it. It's going to cost almost as much as just buying a clutch type from Dr. Diff and rebuilding the chuck.

The BW cone type is a piece of garbage by design.

True, but either way you are looking at bearing replacement anyway, so the cost of the diff unit is extra no matter what route you take.