727 one bad clutch plate. Input to output washer half gone

Is this burned up friction still flat?
There should be a big fat steel plate about .25 inch thick as the first plate in ;
Edit; I mean the first plate to be taken out on disassembly.
was it there? There is plenty of evidence that the steels were only driving a small percentage of the friction material.; this means something was amiss; they were NOT being properly sandwiched.
My first thought, not properly indexed, is not evidenced in these pics.

View attachment 1715881083
In the pic below; what is that serrated business just outside the spring clamp? I don't remember any of my hi-drums having that. Is that what cut your planetary? No, I think that is too low. forget it, lol.

View attachment 1715881107

I would take that Sunshell outta there and have a look behind it, that planetary looks a lil high. But before you do lift up on the planetary and see how much end-play is on that stack. It better be a lot less than the thickness of your broken T-washer, lol. The mainshaft has to free to fall down/back tho; I usually stand the trans up in an old wheel with the M/S suspended, and leaning against the bench, in a corner.
Yes, that's what cut the planetary.