What is the entire tire size? 245/??/16...
That missing number is the sidewall height and is a percentage of the width, which is the first number. Since most of us here run 265/75/16 without issues, it would take a pretty big second number for the 245's to have a bigger sidewall than the 265/70's. If you are mostly concerned with fenders then go ahead and buy the rims because you won't have any problems with that.
My next thought, is that with your tires being 1.5" skinnier, do you really think you will notice the wheel being an inch wider???