I was wondering if a standard 240z can take 17*7,5/8 225,40/45 size wheels ?

Your answer is yes, as long as the correct offset is used. I run 17x8 fr. & 17x9 rear, with 215-40 & 235-40 tires respectively. In addition I've shortened all four struts 1.5" and added coil-overs. Once you get into wider rims you will require coil-overs for clearance.