All,
I just performed this brake upgrade on my 04 FX35. I used the 4-pison calipers from an 09 FX50S which are the same as the G37 I think. Either way I purchased the Front calipers, rotors, & pads from an 09 FX50S (everything is Stop-tech from Rockauto) and they are a direct bolt-on. I paid $360 for the entire front kit. I Keep the rear stock as most of the braking is done from the front. I did upgrade the pads and installed new rotors to the rear while I was at it. I also upgraded all the brake lines to stainless steel lines from Stop-tech. Again everything was a direct bolt-on.
The only issue I had was that my stock 20" wheels didn't clear the large caliper. I had to add a 1/2" or 15mm wheel spacers to clear the large caliper. Below are some install photos. I spent about $600 for everything, front and rear rotors and pads, front calipers, S.S. lines, and wheel spacers. Very cheap from RockAuto.
All I need to do is bleed the calipers and take it out for a test run. I'll let everyone know if it was worth it.
Thanks,
Dan