For many years our Navajos and chieftains cruised at 180 knots, and the P68 cruised at 155 kts.
The P68 is much like a twin engine C206. It will fly from alice springs to Adeelaide (720 nm) at night with a light load, and 200nm with 6 POB.
It is a better short field aircraft than the 206.
Check Australian maintenance requirements before buying a modified aircraft. CASA have some strange ideas about maintenance, even with unmodifird aircraft, and modified ones can be unknown territory. Things like wing spar life may be affected by modifications in Australia. (VG's etc)
Refurbished aircraft may be ok, as long as there are no mods.