We must all be on the same beer!!
Yesterday I removed the seats from my '37 Maple Leaf (Australian Assembled) and removed the fuel tank.
I had to remove 3 large Garbage bags of rats nests , dropings etc, near made me puke.
The Tank straps were secured under the floor by 4 x 3/4 head nuts similar to a Mag wheel nut.
The other protruding bolts with the springs etc are Cab bolts.
Some things on this truck are different to US & Canadian models, in that they were imported as Chassis/Cab and the HOLDEN (GMH) assembled and fabricated the cabs, different door styles, windscreen etc.
All the best with your project.