Gear cluster spacers

I have never seen that. If the thrust washers do no accept that, then it's wrong. How many spacers did you get and were they all the same thickness? Where I'm going is; are they select-fit?
If not select fit then my thought is; any chance one of the needle-bearings fell over, cuz that looks about right for a needle-width...
Wait; those aren't caged rollers are they?
That center sleeve sticking up is just the assembly arbor right?
If yes then the fallen-over needle idea is impossible; the arbor would never fit in there

End play of the cluster is in the range of .015 to .029, so if you set it in the case without the last spacer in there, and get the washers in there, and it falls in with the correct endplay, then the stack-up inside the cluster is too tall, just like you are thinking.
The spacers and sleeve are all hardened materials, and to shorten them, will require grinding, and then lathe-finishing. I think I would allow about .003 per row of needles so with a total of 4 rows, the last spacer should be a minimum of .012 below the end, and inside of the cluster. Make sure all of the spacers are ground flat before trimming the sleeve.