You have options for washers:
- Your local dealer can still order them, part #90201-222F4-00 or 90201-224L4-00 are still available. They are different thickness, but the diagram I looked at didn't specify what.
- Make your own. I'd suggest hardened steel.
Make sure to keep the swing arm centered in the frame by having the same thickness of washers on either side of the pivot.
You might want to replace the MC and hose with a set that is more suited for them bars.
I welded the seat mounts to the frame and fit the seat.
I attached the seat pan/cushion to the base.