I am in the process of researching a weapon system that was tested on the Huey. I read a single article on it, back in the 80s(long before the internet became a thing), and what it was was a large shotgun-type system, the weapon firing something like 12,000 shotgun shells, from three rectangular containers on the lower nose of the Huey, with one box facing forward, while each of the other two are facing at an angle.

I think this was called the XM-277, but that might be completely wrong.

Ultimately, my goal is to build a model for a relative who claims to know everything about aviation and aviation history, especially with regard to the Vietnam Conflict(it was never a formally declared war, and no argument otherwise would change that).

Here you go mate. "MX-215"
https://medium.com/war-is-boring/the-u-s-army-tested-a-helicopter-shotgun-armed-with-1-200-barrels-ce1ca126537d

I think that asking if there are any extant drawings of this, as well as other photos would be unrequited.

However, that looks relatively doable, with a sufficient amount of skull sweat.

And about 90 feet of styrene tubing

You mean, 90 feet of scale tubing.

Now I have to get the hand calculator to figure out how small .25 scales at 1/32. Probably near microscopic.

Any thoughts on the Revell 1/32 UH-1D?

After some careful calculation(Mr. Casio actually did the bulk of the work), each tube has to be something like 1/128(.5/64) in diameter.

It is still relatively doable.

It's ancient and crude, but it's also big and impressive. With a modicum of work, it can be made into an excellent model. Recently produced kits have a lot of flash so you might want to get an older boxing if you can.

Also, don't forget about the forthcoming Kitty Hawk kit and the various 1/35 kits which are generally available from Dragon/Panda.

While any kit, with sufficient attention paid to, can end up with decent results(I built a kit of a MiG 15 in 1/48 scale, in which each wing was in two pieces, the bottom part being the larger, the top part fitting in a wide ditch on the bottom part, which needed a ridiculous amount of putty, the cockpit was little more under a rather thick canopy, and the landing gear a tad less than basic), I'm not worried about claims about the kit's vintage.

I like it.

If you look close at the middle photo, showing the weapon mounted on the Huey, all 4 of the little boxes each have a cover on them. I wouldn't even have to try to make all the little tubes(actually, each one would be a short piece of .020, with a shallow hole carefully drilled. While each once scales to something like .015 or so, .020 would be close enough, unless some enterprising scale critic breaks out the digital caliper and tells me that .005 or so bigger than exact scale size is totally wrong, and that it is not a real scale model as a result).

The more I look at this now, the more fun it appears that I'll be having.