Hi I’m from South Australia I have an 1961 s series that needs tlc

The S-model Australian Valiant (=US '62 model) used the US-type gear reduction starter with 10-tooth, ø33mm drive pinion. The R-model (=US '61 model) used the US-type Prestolite (Auto-Lite) direct-drive starter with 9-tooth, ø25mm drive pinion. Australian AP5 ('63) through VF ('69) Slant-6s used locally-made Bosch direct-drive (9-tooth, ø25mm) or gear-reduction (10-tooth, ø27.5mm) starters; some of the V8s used a version of the Bosch gear-reduction starter with a 10-tooth ø33mm pinion.

OP, Charrlie is right; you'll need to use a starter that matches the flywheel.