David,
As far as I can tell, all the ones in the UK were rebuilt as "Tractor, 4x4, Anti-Tank, 17-pdr". These were based on the Morris C8 2pdr AT Portee, Morris C8/P S.P. Predictor and Chevrolet 8440 2pdr AT Portee, converted into 17-pdr gun tractors after the portee concept became obsolete. If I recall correctly, the original portee body was modified, rather than an entirely new one was fitted. Read Wheels & Tracks issue no. 33 for the full story and photos. The picture below shows a rare surviving Chevrolet 8440 2pdr AT Portee:
Source:
http://www.enygmag.com/military/photos/presveh2a.htm
By the way, the C9/B wasn't an AA gun
Tractor, but a Self-Propelled gun. It had a 40-mm Bofors AA gun fitted on the chassis. There was a CMP variant of this AA truck as well. Picture of the Carrier, SP, 4x4, 40-mm AA (Bofors):
Source:
http://www.trackpads.com/heavymetal/belt00-1.html
Regards,
Hanno