ERF:
This is almost certainally not the 1967 one John remembers.
The chassis number dates this one to just a few weeks before despatch, so it was not hanging about long after the chassis frame was numbered and built up, even though it was an R&D vehicle.
Unless the special cab was built two years prior to the chassis of course. Not impossible?.
Possible, certainly. 
If Jennings were to take on the task of assembling the MW cabs for ERF, they would have been busy making and trying out jigs etc, long before the first vehicles went out the door. If this was not “John’s chassis”, then that may have been the prototype for this one. ERF had certainly identified a market in Australia for low-powered long distance chassis. For what, though- food distribution?