Where COPO's Go To Die

[Too Many Projects]

It looks like it's mostly rust. I would use a wire brush with a rust penetrant to loosen it. Once you have the rust cleaned as well as possible, it may still take light sanding with 400 and water as a lubricant to reveal the stamping. You just don't want to use anything aggressive for sanding.
The stampings for the trans should be on top. It will have a coded assembly date and should have the last 6 numbers of the vin too. They can be almost anywhere, but the top was the most common, usually on the main case, but sometimes on the midplate.

[PapsMaro]

Hard to see

[Too Many Projects]

That's a casting number. The numbers you are looking for are on the axle tube, between the center carrier and the backing plate. They are usually on the side facing forward, but can be almost anywhere on that tube. They will be recessed from a hand held stamp, not raised as part of the casting.


Here's a pic of the assembly code you are looking for.