your tranny can take some wicked launches but can your clutch and rear end? Have you done any work to the suspension? Does that tranny have a trans-brake attached? What RPM does the converter stall at? Is the car actually a 07 Shelby or just a GT? Any other mods done? Tuned?
You should launch at the highest RPM that you can while getting the best 60' times. So, if you spin violently launching from 3000rpm and end up with 2.1sec 60's then drop the rpm till the wheel spin is no longer lengthening your times. Some guys have to flash it from idle, some can wind it up... depends on the car, the track, the tires and the day.
<azz chewing for t3h n00bz)
Lastly, Search and be more detailed with the background info. Questions put like this one only make people mad. You're asking a very technically challenging question to correctly answer but giving us exactly zero detail in the places it matters. We're as likely at this point to give BS advice as good due to lack of detail. </azz chewing>