I have flown Tocumwal/ Bairnsdale and reverse on several occasions, so similar track to what you are asking about. TAS at 140 knots in the RV. The lowest safe for the area is high, over 7,000'. Not sure how long it would take you to get there or what performance you would have. For me its about 70 minutes flight time each way, and not all of that is over the high country.. One recent trip I had over 58 knots headwinds for about 15 minutes. Was fine at 9,000' (IFR). I wouldn't have been comfortable down lower or in a lower performance aircraft. If the weather is even slightly forecast as dodgy I choose a lower route.
You may be going over a Designated Remote Area so would need to check the rules for that and make sure you comply re reporting and equipment. Not onerous but important. You may also need clearance through East Sale Airspace depending on where you're starting/finishing your trip.
And asking for advice is always a good thing to do.