I don't have your model, but if you look at this video and go to 17 minutes and 22 seconds it shows a shot of the washer-dryer closet.
Now, I have a Splindid stackable washer and dryer in my Montana, and judging by video, there should be room for the washer and dryer to fit through the door. However, I question if the dryer will sit on the upper shelf because of the curvature of the front cap.
I think that closet is designed for the washer-dryer combo (one unit) which will sit on the floor.
Before purchasing, measure everything, height, width, and depth. You also need space behind the washer and dryer for hoses and the air vent, so you need more depth than just the depth of the washer/dryer.
Note: as with all the Montana High Countries, the difference between the 330 and the 331 is, the 330 will have a gas-electric refrigerator. The 331 will have a residential refrigerator with an inverter and 2 batteries. Other than that, they are identical.