Spares: Wide Version Swing Arm Measurements

Measured the grey "wide version" swing arm.  End to end is about 8-5/8".  Found a 9" bolt on eBay claiming to be part #90121-028-030, in which case it came out after the 1968 parts guide was published, because that guide only goes up to -020.

Feeling a little compelled to buy it, as otherwise I'm stuck with a swing arm I can never use.