Are you able to push the outer CV joint outwards from under the car towards the hub?
If you can start the nut without the washer under it you may be able to pull out the driveshaft out enough to remove the nut and install the washer under it.

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Fourings

84 Audi Coupe GT with Turbo engine, EFI (buh-bye CIS), Jamex seats, Koni's/H&R's, e-code lights. 210k and counting.
1992 Anthracite 400E, 161k, "Grey Ghost".
1986 VW Quantum Syncro, 192k, gone to the crusher in the sky.
1989 300TE 172k. (Was mine, now also Mom's car)
72 280SE 4.5 (Mom's car)