Ok here's what I got happening. Rust and gears, trying to figure out what to run. I pulled the fresh case apart to run the matched set of gears, instead of mixing them.

Here's the 3 gears I'm looking at in the fresh case I just took back apart:


The far right (front output gear) was the worst one, as seen in the original post. The screwdriver is pointing to the original gear. The one you see in the fresh case is the nice one from the donor case.


But now I see the other 2 gears from the donor case, have some rust pitting as well! As seen here in these pics:




So, the gears that are currently installed in the case right now are the nicest ones of them all. The only change made was swapping the Front Output Gear.

I don't have a matched set of gears where all 3 aren't pitted. Either run it as they are already installed with the different Front Output Gear, or put in the 2 other gears that have rust on them and make them match. I'm inclined to run like it is, but am just curious to what's more important; having nice clean gears as possible, or keeping them matched.