Transformer : 570V to 380 V, 3 Ph
Transformers need to be rated at least the load they supply. In this case, 80KVA would be the dead minimum. Anything smaller than that would burn up after a while.
A typical 3ø industrial service in Canada would be 347/600 volts. So you'll need a 3ø transformer with a 600 volt primary and a 380 volt secondary, and at least 80KVA. The next standard size up from 80KVA is 112.5KVA, but you might be able to find a drive isolation transformer that's a bit smaller.
The primary of the transformer should be delta, but wye will work. The secondary depends on the furnace. If it needs a neutral (4 wire) then the secondary must be wye. If it's 3ø 3 wire (no neutral) then either wye or delta will be ok.
80KW at 600 volts 3ø is about 77 amps; make sure your service can handle this much power.
When buying a transformer, pay attention to shipping costs. A 12.5KVA transformer is heavy; somewhere around 700 - 1000 LBS.
Using autotransformers from 600 to 380 is usually not practical because of the voltage difference, but you might be able to find a used one that'll work. Autotransformers are about 1/2 the weight of others, but are more complex to connect.
Be careful here, the service is 60HZ and the furnace is most likely 50HZ. This will be fine for the heating elements, but if there's a motor or a control power transformer involved, it might not work on 60HZ.