Spook, what about an old CFS/CFA/MFS truck, or if you want bigger, maybe an old airport fire truck?
Thinking of this sort of configuration...
That's probably a new-ish one but you don't see any in service that look old, so they must be somewhere around the place....?
Most (particularly MFS) have dual cab, so that's good.
I'm not taking the mickey with the next pics....I'm not suggesting that your TAFE guys build a replica Cobra Transporter, but they show what sort of structures might be incorporated into the truck:
I hope you find the right vehicle for the job.
Cheers,
Glen