Yes a 245/75/16 is wider and taller than a 225/75/16
245 stands for the width of the tire in millimeters
75 stands for aspect ratio
16 stands for rim size
245/75/16 is 30.46" tall and 9.64" wide
235/75/16 is 29.87" tall and 9.25" wide
225/75/16 is 29.28" tall and 8.85" wide

The stock rims for the 1500 are 16x7 unless its an offroad edition which came with 17x8 rims
I'm not sure if its a sport thing or a towing package as far as what size tire comes with the truck, I know some 4x4's came with 265/75/16 tires, and the offroad edition came with another size

 

The tire your running on your truck now is
275/60/15
10.82" wide and 28 tall
thats the same size tire im using on my truck for the drag strip and they look tiny on my truck but they dont stay on for long