Sorry I can't help you here @ozbucheron - got a lot of stuff...

Sorry I can't help you here @ozbucheron - got a lot of stuff happening, but just a suggestion to go back to the original source data/reports from where these two plans were generated and make sure they are both in the same Austrlian Geodectic Datum?

Its possible some of the older stuff could be in the older AGD66 AMG eastings and northings datum and the newer stuff could/should be in AGD84 AMG easting and northings datum (GDA94 = AGD84/WGS84 and GDA2020 to a matter of 1.5m so not significant) but just remember that tranformation from AGD66 to AGD84 can be in the ball park of 200m NE - might help explain the discrepancies you see?

I remember I went into the weeds about a year ago tracking down the original BHP reports but didn't keep all the data sorry, looks like you have access to it anyway.

I would love to see the original Geophysics report :

Nelson K., Review of open file EM and magnetic geophysical data at Ayra Prospect, GeoDiscovery Group, unpublished confidential report to Castillo Copper Limited, June 2021, 16pp.

as well but I would assume the Geodiscovery Group aren't a bunch of amateurs, and would have double checked all the survey data before even attempting to remodel the geophysics. If they were given the original correct data in the first place, thats why all good geophysical contractors always go back to the original source data from the government/filed previous reports and old data and don't just "trust" the data provided to them by the client (CCZ).

I guess the rotating truth machine will tell us eventually about that reinterpretation of the target vertical depth from 430m to 200m depth but I would sure like to be confident in the location of everything, before they drill the holes, because putting geophysical targets and holes in the incorrect position risks not testing the target properly.