if your doing a basic stateside unit, then just use Korean War figures. The uniforms didn’t change all that much. The only noticeable thing I can think of is that some didn’t have cuffs on the shirts and others did. I have seen both in use at the sametime.
if your doing a Marine 155 unit in Vietnam, of course you have to use the Marine BDU’s. Still you might see a Marine gun manned with guys in the standard BDU’s and then a guy wearing jungle fatigues. Marines were big on flak jackets for some foolish reason.
That Bronco kit begs for the metal barrel, but unless your doing the oddball 100+ that were ordered by the Marines; then go with the M1 barrel. The photo with the open breech depicts a very early howitzer (cannot tell how early by not seeing the jack). The hand wheel in the photos seems larger than life, but it obvious that it correct. That breech is a very early style breech, and those never went into combat much. No big deal as the main difference that the threads were hard chromed. Later they reshaped the mushrum head to be a little more rounded. And even later all pieces were hard chromed. The photo in a full 60" of recoil tells us that he’s just shot a charge seven white bag. Note all the sand kicked up! He’s also violating the number one rule about being an AG. Never ever hold onto the lanyard! Also looks like he’s stradeling the trail with his arm on the wheel. If the howitzer jumps out of the ground (and they do) he’s not going to be feeling very well. Between the trails can be a very dangerous place if your in error.
Lastly; in the box art we see them using a radio. They learned real fast in combat that radios are very problematic in combat. They don’t like the concussion, and are easily jammed. They like the basic field telephone hard wired to a source. They’re pretty much jam proof. I’ve seen one gun crew load from the right, and that’s insane! Load from the gunner’s side. If he get’s in the AG’s way (and he will), somebody is going to get hurt extremely bad. The guy just standing there should have the rammer’s staff in his hands, and be right behind the loader. That round weighs 98lb.!! The illumination rounds can weigh a few more pounds yet. The whole idea is to hurt the other guy and not yourself.