Across the gulf - drop into Karumba and have a coldie at the sunset Tavern, Do the Normanton - Burketown Road, Leichart River, and the gulf road into the NT. Alternatively skip Burketown etc. and drive down to the 4-ways, up through Gregory Downs and onto Lawn Hill and the gorges, then drop down to the bitumen just shy of Camoweal.
The gulf road through Hell's gate up to Borrolloola (McArthur River) is a good drive, but there aren't many places to camp along the way any more. The couple of homesteads that used to cater for it have closed their doors for various reasons. Woologorang Station used to do it but has closed now I think. I think you'd be able to camp on the far side of the Calvert River still. There is a little spot up the far bank on the RHS. The Calvert River is shallow and worth a stop for a cooling dip in the rock pools. The Robinson River, a little further up the road is also not a bad spot for a swim if nice and clear. Have never heard of crocs around there, but you never know.
Lawn Hill and the gorges really are a must though.