Thats cool! Google for "1/48 Monogram Huey" and youll find several build reviews that will alert you to the kits pitfalls.
And the guys are right, it is neither this nor that. The weapons will do for an Army B gunship, even though the ammo belts are wrong - they should be chutes, NOT belts. The grenade launcher is VERY cool but is an Army thing, too. Ray summed it up when he said just do it as a "B", and I'd add leave off the mg's - use the rockets and grenade launcher. But, you'll need Army decals.
Snake is right, I think it's best as an early Marine Corps UH-1E, before the switch to "C" configuration. Make it a UH-1E 'slick', like the one he showed in the top pic. Here's another view of that:
I'll need to get a look at the rescue winch on the forward roof, though. Maybe it'll be in the Osprey book...
Another option I'd like is an Army "B" model air evac or, "Dust Off." They'd look like this:
The problem with that is the big engine intake grill. The Army's was more subdued. These evac birds saved many a man and need to be modeled more, though, so it's a good option.
There are a lot of Bravo scheme options, too. Norway, Spain, RAAN, they all have used them... even the Ventura County, CA Sheriffs Dept.! I found a USAF "Gate Guard" Bravo that would make a kick-a** display. Here's another I like, being an ex-NAV man:
For OOB accuracy, do what Snake says with the kit decals... make it a USMC "slick." If you can find some Army decals, do the Frog rocket/grenade gunship.
For fun, do whatever you want - it still looks awesome with all that ordnance hanging on it. I mean c'mon, a 40 mm auto feed grenade launcher? That is wicked!