I have been in contact with Roy Adair who was an OiC on the PACV during their first tour in Vietnam, I asked him some questions about the cabin layout and he very kindly answered them for me below is his reply.
I have posted this to help anyone else who maybe working on this model.
David - It is my pleasure to do what I can to help you with your project. A little background first. The US Navy had three PACV's for use in Vietnam. They were originally deployed in 1966 and I was a PACV OinC with that unit. At the end our our deployment in December 1966, all three craft and all the personnel were returned to the US. The craft were overhauled and modified and new crews were trained and subsequently redeployed to Vietnam for approximately two more years. From viewing the pictures of the model that you sent, it is the modified, later version that I just mentioned, not the one that I operated. The real giveaway is the deck planks on the exterior upper surface of the hull that allows people to more easily move about when outside the cabin. Another difference is that of the "puff port" located on the port and starboard sides of the hull...these were meant to allow air from inside the cushion to escape under the operator's control to help maneuver the craft at slow speeds. But now I will answer your questions in order:
1. The interior was the color gray
2. The "pilot" (not really a pilot, as that infers aircraft) or operator sits in the right seat and the radar operator/navigator sits in the left seat, looking forward. The picture of your model shows the radar scope on the right, which is incorrect.
3. The normal crew was 4: OiC, nav/radar, engineer, and gunner. Sometimes we would have an additional crewmember such as an assistant gunner or line handler. We could take maybe 2 or 3 passengers inside the cabin, but we did not have the passenger seats that are shown in your model, so passengers would just have to stand. Toward the end of our deployment we operated with US and Vietnamese Special Forces and each of the craft would be assigned a Vietnamese rifle squad. These personnel would ride on the exterior walkway, close up alongside the engine nacelle, and hang onto a handrail. This was before the extended deck were installed as you have on your model.
4. We did not have the helicopter style helmets. As I recall, only the gunner wore a helmet when manning the twin 50 in the turret, but it was just a regular helmet. I think I've seen pictures of the later crews wearing the helicopter style helmets, however. We all wore flak jackets.
5. As for the interior, I already mentioned that the radar should be moved to the left side and the instrument panel to the right. In the version that you have, the passenger seats are probably okay. In the center of the cabin, below the turret, there should be a stand for the gunner. I also see that you have a couple of M-60 machine guns and they would be mounted in the middle windows on both sides of the cabin. In our version of the craft, we had a table at the back of the cabin that ran the full width. The radio was mounted on the table and it also provided room for our nav charts and other paper work.