5L EFI Motors (VN on)

[rallyvan]

So I am taking my van on a 14500km lap around Australia in August as part of the 40th Anniversary of the 1979 Repco Trial. My van's current spec is a worn standard spec 308 and Quadrajet carby with a Turbo 700 auto getting roughly 4km / L or 25L / 100km. Bearing in mind I use the van as a service van for rallies so it has a fair amount of gear in it. On the event I am towing a car trailer as well!
I know a couple of members have vans and or utes with VN on style injected motors in and I am wondering what sort of mileage they are getting?
The EFI motors on paper are a more efficient engine (I am hoping for 8km/L) but I want to see what the real world experience has been before I charge off and source late model heads, manifold, loom etc.

[axistr]

I have a VR 5.0 195kw Club Sport engine in my Torana, and its obviously a lot lighter 1,450kg but on the highway it generally get around 7.8 8.5 km 1lt. Running 3.9-1 diff gears but double OD Tremec T56. sits on 2,100 rpm at 100kph.