I use diesel turbos on gas motors. Used diesel turbo's can be found cheap. I have a HX-35 from a Cummins on a Ford 302. I had a pair of HY-35's, also from a Cummins, on a 327. They are currently being put on a 454 but may be a little small. If they are I'll try some HX-40's or 50's. You need to compare the boost levels and max rpm of the donor and compare that to your project. A 5.9L diesel with 25lbs of boost at a max of 3000 RPM is roughly comparable to your 5.7L gas motor at 12.5lbs of boost at 6000 RPM. Some of the manufacturers have compressor maps on they're sites or offer flow information. The HX-35 flows .46 kg/s at three atmospheres, which, correct me if I'm wrong, converts to 800 CFM at 44 psig.