Hello everyone, I am new to this site and new to posting threads so please be patient. This just seems to be the best way to get a ton of suggestions. Let's start with what I have.
2017 Mustang GT with the automatic transmission and the stock 3.15 rear end.
Right now I am having a Roush phase 2 installed and the speed shop doing it gets about 780-800 out of the complete install which includes the phase 2 kit, cat delete, CAI, exhaust and obvious tune. RWHP usually ends up between 618-635 on their automatics. I am having the suspension replaced which I won't bore all of you with the part specifics as you already understand what tuning the suspension does. The vehicle will be about an inch lower as well. They are installing Nitto 555s all around with 275/40/20 in the rear and a one piece aluminum driveshaft.
Now for my question. With an automatic, with let's say 625 rwhp, a suspension set up, and those tires, what rear end gear should I run? I know the next question will be what am I looking to do with the car? Street, strip or both? Both but I would say 90/10 street/strip. Some of you may know what this combination will do and maybe I will shift into 5th before the traps hurting my 1/4 with let's say a 3.73 but every thread I read talks about vehicles with just a tune so maybe I need to be in 5th? I don't have a clue hence this thread. I understand if this is unknown but any information that can be given will be appreciated. I would like the speed shop to install the gear so I pick it up tuned, with the shift points, and the speedometer calibrated. So if any of you have some winning combinations or great suggestions, please post them. Thanks a ton