The STS camaro kit puts the turbo right under the gas tank. They measured surface temperatures with a probe and there was no change. When the turbo is spooling and making heat, you are generally moving rather quick so there is lots of cooling air down there, especially in our older less aerodynamic cars. Also remember that the turbo can hang down a little and never hit a speed bump as long as it is relatively close to the rear axle. Don't give up on your idea. It is a good one and there are lots of successful rear mount setups out there.
