Static timing is 2 degrees BTDC for 25D4 distributor.
Set it to that and check for pinking under load. Advance timing till it just pinks under heavy load, then retard using little wheel on dizzy till pinking just stops.
A bit of trial and error involved of course.
If using a strobe, make sure idle below 600 RPM and disconnect the vacuum advance, and set for 6 degrees BTDC