Can I change the tire size from 225/65/17 to 245/65/17?

the tires are a whole inch bigger in diameter, which is out of range I would not change. Stick with the tires size that dodge recommends on the door jam.

Ideally, this would depend on what wheels you're planning on using. Locate a wheel with an offset of more than 40mm which would push the wheel out slightly. But according to wheel- size.com the largest stock tire seen on these vans is 235/65/17 so with the correct wheel and offset you can manage the 245/65/17 tires