If it's any consolation, both of my 89's use retainer plates rather than C-clips.
A "quick and dirty" check is to see the brake backing plate - there will be four bolts for the retainer plate, and you may be able to see the retainer plate itself behind the hub.
Failing that, next time you change the gear oil check the side gears - if you see a "pocket mill" recess with a C-shaped washer in it, it's a C-clip. However, the C-clip axle seems to be a late-model thing, and a ChryCo one at that (the 90-down, still being AMC-designed and -specced, don't seem to have it. I don't have C-clips on any of my four - 87, 88, and two 89's.)
Also correct that "D35C" stands for "Dana 35 Custom" rather than "C-clip" - those are housings that were shipped to AMC/ChryCo unstuffed, and final assembly was done in Toledo #2. (Source - ChryCo OEMR Parts Catalogue.)
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