Had mine done a couple weeks back. I went with 3.73's though. IF u are going to pay someone to do it figure $2k-$2300 depending options for everything. I went with BMR bushings and JRE clutches in the LSD unit.
2012: Vmax TBody, CAI w/scoop, Solo HFC, ZL1 FP, Magnaflow TruX, Dynomax VT, RX catch can, HP Tune, Throttle Contoller, BMR; Springs, Sways, Trailing Arms, Toe Ends, & Safety Loop, Koni str.t, Pioneer Z150bh, Phoenix Gold Sub, Hertz speakers & 5ch Amp, SS rear with 3.91 gears w/Eaton TrueTrac, and BMR bushings, Baer Decela Rotors, Goodridge brake lines, Brembo(GM) 4 piston calipers, Hawk Ceramic pads, and Michelin PSS tires, N.O. Nitrous, JacFab 3/4" intake spacer, and ported intake. 345RWHP/354lbsTQ 12.8@108