got my 3.90 rear installed this weekend now the track is on vacation until Aug when i get the second run ( 1st run 100% stock srt6 13.3@ 105 60' 1.98 street tires) I will be running street tires this year at the track here are some pic of the rear end and my rear suspension. this time it took us less than 1 hour to swap the rear. the car does feel great with this rear , did have a short burst with a LOUD mustang we were doing 60 then took off i pulled him at, 80 I let off . he just gave me a thumb up , i slowed to 60. oh at 70 i am doing 3000 rpm 80 am doing 3400 . what a difference this gear makes love it