I have uploaded photos of my rear diff. when I took it apart to add an lsd. You will not leave two even marks when the traction control is switched off, the only way
I can run autocross it without having the computer shut the throttle shut down. Mine is a 2005 SRT-6 with the 5 speed auto. The rear took me 5 hours to pull the independent rear suspension and then reinstall all of the struts and exhaust.

The Phantom Grip that I installed will leave two marks about the same length and with lots more traction take-off. The factory applies the brakes to the spinning wheel in a stock car untill the opposite wheel beaks loose then clamps that one in milliseconds, causing that harsh shutter on take-off like its jumping up and down.

I have been there and done that, the stocker is all electronic, like my ex's GT mustang. There is no posi or lsd, among other reasons than the low cost, posi rears require more skill to keep from going in circles like my 73 CHALLENGER 6 pack. In a turn the 'lsd', will drive , spin both wheels and you will go sideways unless you have drifting practice. Woody