Could the different length be absorbed simply by the thickness of the new bushes and where the washers sit?
If you put the flatter washer at the top, then the bush, then the curved washer, with the curve facing down to facilitate movement. Then slide the pin through the axle, put the next curved washer on, curve facing up, then the bush and then try a flat washer and a nut.
The movement will be allowed by the curves and the extra pin length will presumably be absorbed by the bush and washer arrangement. The shoulder on the pin will perhaps act as a stop for the final washer and nut.