Depending on how much extra you need but I would be looking at a 50mm block for the van tow hitch, its legal , having a long plough shank hanging down from the Cruiser is not ideal and defeats the whole purpose of having an Outback.............
Get your tape measure out, on flat ground measure Cruisers ball height then with van level measure to similar point on vans tow hitch, ideally tug should be about 25mm higher than van, (if its the same height it will be too low when hooked up) work out what the difference is and that will give you the extra height you will need which pertains to your set up, no 2 set ups are alike............ then you can look at a block to lift your van hitch, much cheaper and much better or you can go for a drop shank which will give you the height you need they come in various lengths, they aren't vehicle specific but you need to know the depth of your housing on tow bar as some are open and some are blocked off, Hayman Reese have a wide selection .
Myself I would go for the van hitch lift block ......... I assume you have a draw bar which has the hitch mounted basically at the bottom of the bar, a stupid idea for an Outback and more suited to towing with a car...... some even weld a new mounting plate on top and fit the hitch...........