I have no personal experience with the 292.
My shop "truck" for years was a extended wheelbase 1979 van with a 300 CID six.
Original carb was a single barrel Holley.
Replaced the Holley with an Offenhauser 4-barrel intake, and a Carter AFB 9400s (400 CFM) carburetor.
If I had been blessed with only the 7-9 MPG suggested in this thread, I would have driven it into the lake, and left it!
And yes, I did modify the AFB for manual choke, and maybe did a wee bit of recalibration on the carburetor.
I won't post the fuel mileage, but the van (loaded) made it from Eldon, Missouri to the Chickasha, OK swap meet without a fill-up, and driving at the speed limit (65/70 in Missouri, 75 in Oklahoma). The fuel tank was original. If anyone is interested, you can look up the miles, and the fuel tank capacity, and do your own math.
Not familiar with the Aussie intake; as I stated, I used an aftermarket Offenhauser.
Jon.
