I thinks it's fair to say they're a bit shagged

The old spokes were rusted in place to the spoke nipples. Could barely turn it no matter how much WD40 and/or heat was applied. Had to cut them all off in the end sadly.

Measurements

Measurements derived from some cut and removed spokes and nipples.

Super technical drawing here

EDIT: 2021/01/31: Got those rear spoke sizes slightly wrong. There’s two different angled and lengthed spokes on the rear. Had to cut them off so can’t confirm what they are but the supplier has the sizes for an XT600 with rear drum which should be correct.