Lowered on coils with a 9.5+12 I'd run a 245/40 up front, with an 11+15 I'd go 285/35 out back. You'll have some stretch but nothing crazy, all depends on how low you go, how much camber you want and if you want the meaty look or stretched.
Here is a helpful and fun link, play around with it and see what you like.
1010TIRES.COM - Wheel Offset Calculator