The LVT-4 was the later version with a rear ramp (known as 'Buffalo' to the British); including this would clearly require too many parts. That's not the version I meant.
The LVT-2 was the vehicle upon which these 2 fire support versions were based. It had the same layout, with the engine in the rear. The driver's compartment was different, being taller and lacking the roof hatches. And of course it had an open-topped troop compartment. But it's essentially the same vehicle from the hull top down - aside from the interior (which I'm sure Rubicon could include with some clever moulding), it wouldn't require a lot of additional parts.
The LVT-2 wasn't armoured, although they were often up-armoured in field workshops (and was later manufactured with an armoured driver's compartment). So an armoured version, the LVT(A)-2, was developed. This had the same driver's compartment as the LVT(A)-1 and LVT(A)-4. Apparently the LVT(A)-2 was only supplied to the Army, although from photos I it seems to have seen service with the Marines too.
It's also worth remembering that the LVT(A)-1 was fairly quickly superseded by the LVT(A)-4, although not completely. The 37mm gun wasn't very effective in providing fire support. So it wasn't particularly successful at what it was intended to do. It was the LVT-2 which was the most numerous amtrac type used in the Pacific, and the vehicle most wargamers will want in quantity. That should translate into higher sales. I've noticed that the response to this kit on the Facebook site is also to request a troop carrier version.
