Short wheelbase, 20" wheels... looks like cab 11/12 doghouse... and the rear wheel arch looks suspiciously gun tractor. At a guess I'd say it could've started out as a 7A2 or something similar. Even the fuel tank has the filler in the right place.
It's facing the opposite way, but have a look...
http://imagecontrol.com.au/oldcmp/Im...act/cgt11b.jpg
Only thing is it looks like the sheet metal has been replaced around it - the piece between where the passenger door is a bit longer, and also the door above is missing.