I have an 08 g35x all stock, this weekend i will be install tein h-tech springs. I just bought a set of 19x8.5 wheels. Offsets are +30 I want to know if I can get away with 225/45r19 all 4 corners instead of going 245/40r19?

 

That won't be a problem, would be a preferred size for winter tires, but if you're planning on All-Season or Summer tires the 245/40 will be a better choice for the rest of the year.

Be sure to get your car realigned before putting many miles on your new tires, having bad toe specs will really eat up tires.