Another Wheel size/offset question

[driftastyle]

I am thinking of running a set of 18x8 wheels on my S14, I haven't decided tire size yet. My car is lowered on eibach sportlines with no other suspensions mods to date. I am planning on buying a set of gp sports coil overs later. What tire size should I run and also what offset? They are offering +40 & +30 offsets. Not sure if they make any other offset for the wheel.

[Steeles]

get at least 9 inch wide wheels (for 18s) and as close to a 20mm offset as possible.