The FAM calls it a Pin Lock (PN 359380). Shown on Section 5, Sheet 2.00.

I'm not sure a C-clip would work, but it might. I don't recall exactly what the end of the shaft looks like, but the "Pin Lock" is weird. It's soft metal and bends pretty easily.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.