This is the wagon floorpan, normally hidden under the load area floor, which is a removable wooden panel that sits at the level of the metal crossbar in the middle of the picture. This is basically the same arrangement as the lift-up panel in the load area at the back of a wagon that gives...
Chopping a wagon down into a ute might not be as hard as you think - the utes were actually built on a wagon floorpan. Main differences are the rear quarter panels, the bulkhead behind the seats, and the extra panel pressings to create the 'extra meat behind the doors'.
I've got a 1966 VC...