[DVC]

245/40-18 is a good tire size choice; plenty of rubber for grip, and common enough that you can find most tires available, and at reasonable prices.

As for wheel size, if you want to go 9.5 square, you will need some additional camber up front (at least -2.0 degrees total to be sure - a few guys here have done it). I went with 9" ET42 wheels (Apex ARC-8) all around, and the fit was good*; there was a bit of room left over for fender clearance, so ~5mm less offset should be OK.

* My fit is slightly different than most, because I installed the OE swivel bearing (camber) hubs, which angle the front wheels inward -0.5 degrees relative to the struts... which means I have about 5mm less clearance to the strut, and more to the fender. So I ended up fitting 10mm spacers up front, and 12mm spacers in back, to make for a verrrry aggressive fit (just barely clearing the fender on full suspension compression).