A vendor sent me wrong wheels but if they will work id rather make them work. I ordered RC10 in 19'' & they sent me the far more expensive RF2 in 20'' their loss & they are willing for me to keep them but im not sure these offsets will work on my 2011 G37X Sedan

Rear 20x10 +42
Front 20x9 +40

Any advice is greatly appreciated

 

Yes those will work, you'll just have to be careful w/ your tire sizing.
This will be the best combo for fit and AWD compatibility

245/35/20 front 285/30/20 rear will get you a 0.07% variance front to back which is awesome, your rear tire will be close to the fender but will tuck just inside. I run 285/30/20s on 10" +45 and have about 7mm inside the fender, I was running 295s in back and still had a couple mm.
Are you going to be lowered? If not I would consider a drop as the 20s will look a bit off at stock height.

 

yes I certainly plan on lowering. was thinking 275/30/20 & 245/35/20.

 

That's not a great combo for AWD, your rear tire is almost 1% smaller than your front and since it wears faster than the fronts your variance will be over 1% in a short time, and this will typically cause issues w/ your AWD setup at speeds over 75-80 mph. If you want to run 275s in back a much better combo would be to run 235/35/20s in front 275/30/20 in back, this will get you back to that 0.07% variance
BTW, nice wheels, those Rohannas have some nice concave sets.

 

Pictures please.