The Rivian one was designed for Amazon specs. The Ford one is half the cost of a Rivian R1T. This is simply price economics. Amazon wanted to maximize space for packages, not batteries. They have charges at their warehouses and these are charged likely at night for off peak rates.

If we are talking about just an ambulance, the range could get higher, but there are diminishing returns eventually for a giant square so it probably needs an aerodynamic redesign.

I see I misunderstood the question & context. The rivian delivery van is about 100 miles apparently, but that's only because the customer, amazon, gave them specs to meet. All they have to do is add more batteries to get more range. I could pull the rivian ev delivery truck on a trailer behind my r1t and get 150 miles easy, and at slow city speeds probably more. My truck probably cost a good bit more than a delivery van, but has better specs.

I thought the question wasn't about the delivery vehicle, I thought it was asking about rivians in general. There's nothing limiting that range inherently, it doesn't have the greatest aerodynamics, but the goal is carry all those packages.