http://www.1010tires.com and use the tire size calculator. Put in the oem tire size and what size you are looking at. If less than 3% difference than oem, you will be fine.
This info is from the calculator:
245/40/19 fronts
265/35 or 275/35/19 rears
the 225 tire is a bit narrow IMHO for the g37s front wheel and the 245/40 are too narrow for the rears.