Well I thought I had posted a welcome reply a few days ago but its not on here !!! No idea why but welcome Simon, you have got yourself a nice machine and looking at the dials it is Im sure Imperial, better IMO because the “metric” Myford’s are not truly metric. Both the lead screw and gearbox remain imperial but they do fit a lead screw handwheel that has the nearest metric divisions.
My choice is to convert any metric drawing dimension to imperial and use the machine as is, the rust will be a metric component.
As for screw cutting metric threads here are some links to previous threads on this subject but be aware you cannot use the thread chasing dial for metric threads as you would for imperial — there is a workaround that can be used for cutting up to a shoulder. I have a write up done many years ago but now there is a video explaining the process as well.
https://www.model-engineer.co.uk/forums/topic/myford-33t-and-34t-gears-for-metric-threads/
https://www.model-engineer.co.uk/forums/topic/myford-metric-lathe-leadscrew/page/2/
https://www.model-engineer.co.uk/forums/topic/availability-of-a-t33-t34-myford-change-gears/page/2/
https://www.model-engineer.co.uk/forums/topic/thread-cutting-2/#post-204892
John