IMHO the 3.91 is to low. With a redline of 6200, a termed TKO600 and 315/35/17 tires my shift points are 42, 64, 95, 121, 148. At least according to this site:
http://fitbodyshop.net/gear/index.php. If there is a lower LSD I would choose that, but you definitely want LSD. If I had bought new, I'd put a Quaife sequential and probably a 3.73, or lower.