The pickup bed (usual) looks like this.
The bed as appears above is "looking back" from the cab. The panel with the square is the hinged tailgate. You will note at the front right and left lower corner what appears to be wood? This is actually the support wood and the "Z strip" I mentioned is on the outside of these wood pieces.
You will note the square metal piece in the center. This give clearance on the frame "hump" of the rear cross-member which otherwise would hit the wood slats.
The wood floor was hardwood of some sort. Maple is commonly used, possibly poplar. Many restorers who go the "natural" look use oak - but the natural look is not correct. The entire bed was assembled by Ford as a unit and then painted the upper body color - INCLUDING the wood. Rock Moss Green is the usual color but there were other standard colors for pickups.
The bed slats are held together by metal strips bent roughly into a flattened "U" the horns of which fit into sawn grooves in the wood strips. A line of bolts, nuts and "keeper washers" on the underside hold it all together.
The bed metal is riveted together and presents as a unit as you see here. Bolts and wood undercarriage/spacers is how it is attached to the frame. Some pickups have a U-shaped channel (horns of U facing "up") between the body rear and bed front. Many don't have this channel.
The beds are reproduced and available for not too large money here in the US. I expect you might pay as much in shipping to Oz as the price to buy here.
You can buy the parts and assemble it yourself. A bit labor intensive but shipping might be more reasonable as a "knock-down."
Or - an alternative - make your own? Starting with dimensions, you can make up a wooden or "Model T" type bed which will simulate what might have been. A very good design of Model T bed is out there ready for reverse engineering.
Joe K