What part was this shrapnel before it ended up in my transmission pan?

[the_nutt]

First off, hey there. I'm Cody from Austin, Texas. I've had a couple square bodies, but have always wanted a '72 Cheyenne. I have a '72 Yamaha XS650 that I've been wrenching on, and I found a cheap long bed that was mostly there and went for it. Psyched to get started.

Now, the bad: truck made it from Houston to Austin, but started shifting weird about 15 miles from home. At about 1/4-1/2 even throttle it would shift from 2nd to 3rd, then back and forth between 2nd and 3rd once or twice, and finally stay in third.

Got under it and confirmed it has a Turbo 350 transmission (TH350?) by the square pan and 13 pan bolts. Fluid was dark and smelled burnt, and even after adding the fluid that was in the pan/filter to the mix looks like there was barely ~1.5 gallons of ATF drained/accounted for.

The real news is the shrapnel that was in the pan, and that fell out of the transmission once the filter was out of the way (attached below).

Any way of identifying what part this used to be?
Is the transmission shelled, in need of a rebuild?
Any other thoughts? Why is Big Bird so damn big?

Thanks in advance for any help. Really looking forward to getting this thing back on the road, reliable, and cruising!

Cheers,
Cody