If you make it a "Leave pheasants nest at X o clock sharp" time that will help, cause there's always someone who comes late.
Its too far for most skylines to go to make 642k's on one tank, so a stop will be needed, here's where you lose the time. Some people wont like Shell, some wont like BP etc and will want their own blend (not that it matters on light constant throttle highway cruise), if the group has to stop at 3 servos instead of 1 it takes ages out of the travel time.
My suggestion is that you make servo stops known in advance that the group stops at, so from the outset everyone knows what the fuel strategy is. Like this;
Everyone can top up at the start point (its a mobil), so;
Start point to meet point at Yass is 206km
Top up at Yass
Yass to Albury is 279km. Here is a good chance for food if hungry
Albury to Shepparton is 174km
That way there's no chance of anyone running out of fuel, it doesnt feel like a long drive for those that arent used to interstate drives and you'll get there in decent time