Mystery GMC Tractor/Trailers

[David_Hayward (RIP)]

http://clubs.hemmings.com/clubsites/...ysterygmcs.jpg

This mystery is really killing me it seems and the mystery gets deeper. Note the 1940 Model GMC Tractor-Trailers, but none were ever offered like that on the civilian market and none were apparently on the census list either. A close up I have seen shows these to be civilian registered at the time. Note the Caterpillar?? ex-tractor unit fixed to the trailers with some form of generator by the side?

I wondered whether these were demobbed units, as obsolete and the suggestion was that they were used by the Ministry of Food. This shot was circa 1943-44 so these were not new outfits.

However this combo was used at least as Chevrolets assembled by GM Continental, and I wondered if these were diverted orders or prize seizures [there were we know seizures of GM trucks meant for Denmark and Norway, in 1940]. The following information may help. The top is a census listing for an odd contract whose format I have never seen before, for SUPERIOR COACH trucks:

L 6245464 to 6245493 - SR/31211/1 Lorry 6 ton 6 x 6
2 ½ Ton 6 x 6 Workshop (for Radar A.A.)
The next sequence is for GMCs to the same contract:
L 6245494 to 6245523 - SR/31211/1 Lorry 6 ton 6 x 6
Generator (For Radar AA)

Could the GMCs be the latter....by then obsolete? There never was a GMC 6 x 6 6-ton...could it have been 4 x 4 -2?

Superior Coach I think built bodies on GMC chassis, but not trucks themselves. The chassis could be ACKWX-353 6 x 6, ex-French. I had thought at one stage that the tractors were 6 x 4 AFWX-354 as per the flatbed in the extreme background, with the rear chassis chopped and fifth-wheel added.

Any thoughts please?