In order to mount the GT3 muffler at proper height for the cutout the engine carrier had to be backdated to 3.2 style then heavily modified. About 3/4″ additional clearance was needed to give an air gap to the rear bumper.  A mount had to be designed as well.   We had originally planned on using a dusal mode exhaust with factory style valves to block off the lower (almost direct) outlet however  there was no spoace, we needed an additional 2″ or so per side to install the valves.  SHown at bottom.  Electricaly operated valves which are much thinner are also available but i have heard from several sources that these are unreliable.