So I was taking a look at the Q70 forum and read a thread about the sport mufflers. The design looks very similar to the G's axle back setup. Has anyone ever done a comparison of the size/length of the axle backs between the two cars?

 

I hate to revive a old question, but was wondering the same thing. Besides the flange, the mounting points are in the same direction, but can't tell the length of the muffler in proportion to the stock G37 sedan's muffler. I have the Nismo 370z's H pipe, so if these mufflers fit, I wouldn't mid having the back half of the stock mid pipe modified so that it goes into a flange and I can do a direct bolt on, that and remove the step down put from the center resonators. Looking at the stock mufflers of the G37 vs the M37/M56/Q70, they look the same besides the addition of a flange to the mid pipe.