Hi,
The mustang is a fairly heavy car, I would go with 3.70 gears
The gt "p" heads are a good street head, have 180 cc intake runners, don't go bigger or you'll lose bottom end to get that stang moving. Also go with a little better cam, comp cams 270 H magnum is a good alround cam. RPM intake is good, but a performer would work better on the street to 5,500 rpm.
Perry.
