Oooh, more gun truck fun!
1) "Nancy" was made from the original AFV Club M35A2 Deuce. I first backdated and converted the A2 to an A1 and then "Nancy" back in 1996. Over the years I gathered more information on the vehicle and in 2000 I disassembled this model and rebuilt it into what's shown here, with a new M55 Quad 50cal Trailer, because of new information I found on the gun truck. My original configuration (as presented in the new AFV Club kit) was not correct. So I took the opportunity to restore the entire model instead of just replacing the Quad Turret.
2) All gun trucks were not black. The early vehicles were left OD Green. As the armored convoy escort concept evolved, so did the colorful nicknames and paint schemes. The second generation Deuces and M54 5-ton trucks were typically painted black overall. The color photos of "Nancy" from 1968 shows she remained OD Green. Photographs of specific vehicles are critical to get those details down.
3) All the artwork was handpainted - do you mean my artwork on the model - or the real vehicles? The real vehicles were done by the crews themselves - a testament to their talents. Also pay close attention, as when the trucks return from their convoy runs, often battle damage necessitated replacement of parts and equipment - and paint schemes changed too. When trucks transferred to another unit - the name was often changed too. If you meant my miniature, I created the artwork by hand, scanned it into my computer, processed the image with Adobe PhotoDeluxe, and printed it on decal sheet for application to my model. There was no decal sheet for "Nancy" prior to the AFV Club release.
4) The M55 Quad Turret is Tamiya's older M16 MGMC turret with a scratchbuilt Trailer based on Kirin's resin example designed by Chris Mrosko. The Kirin M55 Quad Trailer is really, really, difficult to find today, as it has been out of production almost 10 years now. The 40mm Ammo Cans were Verlinden parts with scratchbuilt cradles. To model "Nancy" you can't use the old drum canisters - she wasn't equipped with them.
5) Yes, all third generation gun trucks (M113 APC Hulls) were based on M54 5-ton trucks. They asked a lot of the Deuce - but not THAT much

. The M54 quickly took over the convoy escort role as they could carry the weapons, ammo, and sufficient armor plating to protect the crew without wrecking the vehicle in the process. However, the powerful anti-aircraft trucks equipped like "Nancy" kept the Deuce in the mix too. Anti-Aircraft vehicle conversions were done on both the Deuce and M54 5-ton trucks - and both participated in the convoy escort role when the threat of North Vietnamese air attack subsided. These were standard AA trucks as used in artillery units - and not specifically modified for a gun truck convoy escort role. The AA trucks got nicknames and flash paint schemes because the Artillery guys didn't want to be outdone by the Truckers. When the MP's joined the convoy escort role, units supporting the 8th GP added a little flash to their V-100's too with nicknames and a yellow "cheater stripe" down the sides of the armored cars matching the yellow hood bands on the noses on 8th GP assigned gun trucks.
As Tread pointed out - "The Big Kahuna" was a special truck in that he was (I believe too from accounts of the Veterans who were there) the first of the third generation gun trucks - the first vehicle to mount the M113 APC Hull in his cargo bed. Of all the named gun trucks - I think his was the most appropriate. "Kahuna's" markings were really subdued and understated - contrary to the flashy trucks like "King Cobra" - probably the only thing that stood out on it was the number "1" he carried for a brief period of time signifying him being the first of a new breed.
Hope I hit on all the questions above. Gun Trucks really interest me because they are the armor modeler's equivalent to the aircraft modeler's famous fighter plane. No two gun trucks are alike. All are individual creations, and all changed and evolved during the War. Armed with enough photos, you'll be able to notice the changes to a particular truck, and this is the fun part of the research. A fantasy truck is a cool expression of the art of armor modeling, but there is so much on the real vehicles that it would be a shame not to select one and build to keep the memory alive...
Gunnie
Gunnie