What size tires?

Hi,
Looking to swap out the slicks on a Dart I recently purchased. The slicks are 10.5/28.5 -15 on a 15X10 rim with a 3 1/2 offset.

The front I am swapping to a 15x4 rim with a 2 1/2 off set.

What size tires should I put on these for the street?

Thanks
Ken