[How do I?] align existing hole pattern to rotary table

[blaser.306]

I may just be "under thinking this" why don't you zero the table degree markings first, then indicate the part to the RT may be overly simplistic but could work?

 

[ezduzit]

You do not need a rotary table at all to do this job. Simply make a tracing of the chuck's hole pattern, referencing to the ID. Then transfer the holes from the tracing to the backing plate, locating off the existing holes.