Rear swinging arm mounts?

[martin.herwitson]

The bolts holding these arms onto the rear beam look to be eccentric? I want to strip the full axle for a strip down re-furb so if I mark the original position carefully will the setup be o.k. on reassembly or will adjustment be required?
Anyone know how to set this back up correctly once it's reassembled? I must be getting old cos I usually strip it all into component parts and then ask