Well, I couldn't wait any longer, so I have reassembled it without those two spacers. The splined axle seems to go far enough into the driveside crank for it to be secure now and the chainline looks pretty similar to with the M730 crnaks/122.5mm BB that came off, so I guess that's what those spacers are for. I'm just waiting for a replacement bolt and washer to tension the driveside cranks and I'll take a photo.